diff --git a/Sprint-1/fix/median.test.js b/Sprint-1/fix/median.test.js
index 21da654d7..8d948fd46 100644
--- a/Sprint-1/fix/median.test.js
+++ b/Sprint-1/fix/median.test.js
@@ -47,4 +47,4 @@ describe("calculateMedian", () => {
   ].forEach(({ input, expected }) =>
     it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
   );
-});
+ });
diff --git a/Sprint-2/debug/address.js b/Sprint-2/debug/address.js
index 940a6af83..a40612037 100644
--- a/Sprint-2/debug/address.js
+++ b/Sprint-2/debug/address.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+// address is object so you can not reach the values by index you can use address.houseNumber or address[houseNumber]
 // This code should log out the houseNumber from the address object
 // but it isn't working...
 // Fix anything that isn't working
@@ -12,4 +12,4 @@ const address = {
   postcode: "XYZ 123",
 };
 
-console.log(`My house number is ${address[0]}`);
+console.log(`My house number is ${address.houseNumber}`);
diff --git a/Sprint-2/debug/author.js b/Sprint-2/debug/author.js
index 8c2125977..cd5b676b4 100644
--- a/Sprint-2/debug/author.js
+++ b/Sprint-2/debug/author.js
@@ -1,5 +1,5 @@
 // Predict and explain first...
-
+//objects are not iterable in JavaScript.
 // This program attempts to log out all the property values in the object.
 // But it isn't working. Explain why first and then fix the problem
 
@@ -11,6 +11,6 @@ const author = {
   alive: true,
 };
 
-for (const value of author) {
+for (const value of Object.values(author)) {
   console.log(value);
 }
diff --git a/Sprint-2/debug/recipe.js b/Sprint-2/debug/recipe.js
index 6cbdd22cd..9b3e356a7 100644
--- a/Sprint-2/debug/recipe.js
+++ b/Sprint-2/debug/recipe.js
@@ -1,4 +1,5 @@
 // Predict and explain first...
+//${recipe} will not give us the ingredients
 
 // This program should log out the title, how many it serves and the ingredients.
 // Each ingredient should be logged on a new line
@@ -10,6 +11,8 @@ const recipe = {
   ingredients: ["olive oil", "tomatoes", "salt", "pepper"],
 };
 
+const ingredientsList=recipe.ingredients.join("\n");
 console.log(`${recipe.title} serves ${recipe.serves}
-  ingredients:
-${recipe}`);
+  ingredients:\n${ingredientsList}`);
+  
+
diff --git a/Sprint-2/implement/contains.js b/Sprint-2/implement/contains.js
index cd779308a..e822b5ce9 100644
--- a/Sprint-2/implement/contains.js
+++ b/Sprint-2/implement/contains.js
@@ -1,3 +1,29 @@
-function contains() {}
+function isObject(value) {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
 
+function contains(obj, prop) {
+    if(!isObject(obj)) throw  new Error ("Invalid input");
+    
+ // return Object.keys(obj).includes(prop);
+ return Object.hasOwn(obj, prop);
+}
+
+ console.log( contains({ a: 1, b: 2 }, 'toString'));
 module.exports = contains;
+
+
+//Does the following function call returns what you expect?
+
+ // contains({a: 1, b: 2}, 'toString');
+// returns false for inherited properties
+
+
+//How to determine if an object's property is its own property or an inherited property in JavaScript?
+// by using hasown method.
+
+//Does your test correctly check whether the function can detect the given object is an array?
+//Yes, the test correctly checks that the function can detect when the input is an array.
+//it("throws an error when the first parameter is not an object",()=>{
+ //       expect(()=> contains([],"a")).toThrow("Invalid input")
+ //   });
\ No newline at end of file
diff --git a/Sprint-2/implement/contains.test.js b/Sprint-2/implement/contains.test.js
index 326bdb1f2..78c5528b9 100644
--- a/Sprint-2/implement/contains.test.js
+++ b/Sprint-2/implement/contains.test.js
@@ -20,7 +20,6 @@ as the object doesn't contains a key of 'c'
 // Given an empty object
 // When passed to contains
 // Then it should return false
-test.todo("contains on empty object returns false");
 
 // Given an object with properties
 // When passed to contains with an existing property name
@@ -33,3 +32,31 @@ test.todo("contains on empty object returns false");
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
+describe("contains", () => {
+    it("throws an error when the first parameter is not an object",()=>{
+        expect(()=> contains([],"a")).toThrow("Invalid input")
+    });
+
+  it("contains an empty object returns false", () => {
+    expect(contains({}, "a")).toBe(false);
+  });
+
+  [
+    { input: { a: 1, b: 2 }, prop: "a", expected: true },
+    { input: { a: 1, b: 2 }, prop: "b", expected: true },
+    { input: { a: 1, b: 2, c: 3 }, prop: "c", expected: true },
+  ].forEach(({ input, prop, expected }) => {
+    it(`returns true when the property exists in the given object , for object ${JSON.stringify(input)} with property "${prop}"`, () =>
+      expect(contains(input, prop)).toBe(expected));
+  });
+
+
+  [
+    { input: { a: 1, b: 2 }, prop: "c", expected: false },
+    { input: { a: 1, b: 2 }, prop: "e", expected: false },
+    { input: { a: 1, b: 2, c: 3 }, prop: "w", expected: false },
+  ].forEach(({ input, prop, expected }) => {
+    it(`returns false when the property non-existent in the given object , for object ${JSON.stringify(input)} with property "${prop}"`, () =>
+      expect(contains(input, prop)).toBe(expected));
+  });
+});
diff --git a/Sprint-2/implement/lookup.js b/Sprint-2/implement/lookup.js
index a6746e07f..25798767e 100644
--- a/Sprint-2/implement/lookup.js
+++ b/Sprint-2/implement/lookup.js
@@ -1,5 +1,10 @@
-function createLookup() {
-  // implementation here
+function createLookup(myArray) {
+  if (!Array.isArray(myArray)) return "Invalid input";
+  const myObject = {};
+  for (const pairs of myArray) {
+    myObject[pairs[0]] = pairs[1];
+  }
+  return myObject;
 }
 
 module.exports = createLookup;
diff --git a/Sprint-2/implement/lookup.test.js b/Sprint-2/implement/lookup.test.js
index 547e06c5a..3bad8c29c 100644
--- a/Sprint-2/implement/lookup.test.js
+++ b/Sprint-2/implement/lookup.test.js
@@ -1,6 +1,33 @@
 const createLookup = require("./lookup.js");
-
-test.todo("creates a country currency code lookup for multiple codes");
+describe("createLookup", () => {
+  it("creates an object from country/currency pairs", () => {
+    expect(
+      createLookup([
+        ["US", "USD"],
+        ["CA", "CAD"],
+      ])
+    ).toEqual({ US: "USD", CA: "CAD" });
+  });
+
+  it("returns an empty object for an empty array", () => {
+    expect(createLookup([])).toEqual({});
+  });
+
+  it("returns 'Invalid input' for non-array inputs", () => {
+    expect(createLookup("CYF")).toBe("Invalid input");
+    expect(createLookup(123)).toBe("Invalid input");
+    expect(createLookup(null)).toBe("Invalid input");
+  });
+
+  it("overwrites repeated keys with the last value", () => {
+    expect(
+      createLookup([
+        ["US", "USDxx"],
+        ["US", "USD"],
+      ])
+    ).toEqual({ US: "USD" });
+  });
+});
 
 /*
 
diff --git a/Sprint-2/implement/querystring.js b/Sprint-2/implement/querystring.js
index 45ec4e5f3..4347e6d4a 100644
--- a/Sprint-2/implement/querystring.js
+++ b/Sprint-2/implement/querystring.js
@@ -6,11 +6,16 @@ function parseQueryString(queryString) {
   const keyValuePairs = queryString.split("&");
 
   for (const pair of keyValuePairs) {
-    const [key, value] = pair.split("=");
+    const [keyBeforeDecoding,...rest] = pair.split("=");
+    const valueBeforeDecoding=rest.join("=");
+    const key=decodeURIComponent(keyBeforeDecoding);
+    const value=decodeURIComponent(valueBeforeDecoding);
+
     queryParams[key] = value;
   }
 
   return queryParams;
 }
+console.log(parseQueryString("tags%5B%5D=hello%20world "));
 
 module.exports = parseQueryString;
diff --git a/Sprint-2/implement/querystring.test.js b/Sprint-2/implement/querystring.test.js
index 3e218b789..97a2a5a7e 100644
--- a/Sprint-2/implement/querystring.test.js
+++ b/Sprint-2/implement/querystring.test.js
@@ -5,8 +5,24 @@
 
 const parseQueryString = require("./querystring.js")
 
+test("returns empty object for empty querystring", () => {
+  expect(parseQueryString("")).toEqual({});
+});
 test("parses querystring values containing =", () => {
   expect(parseQueryString("equation=x=y+1")).toEqual({
     "equation": "x=y+1",
   });
 });
+test("handles key with no value", () => {
+  expect(parseQueryString("flag")).toEqual({
+    flag: "",
+  });
+});
+test("parses multiple pairs when one value contains '='", () => {
+  expect(parseQueryString("user=ahmad&equation=x=y+1&city=Manchester")).toEqual({
+    user: "ahmad",  equation: "x=y+1",   city: "Manchester",
+  });
+});
+test("Handling URL-encoded query string",()=>{
+expect(parseQueryString("tags%5B%5D=hello%20world")).toEqual({"tags[]":"hello world"})
+})
\ No newline at end of file
diff --git a/Sprint-2/implement/tally.js b/Sprint-2/implement/tally.js
index f47321812..a306879ca 100644
--- a/Sprint-2/implement/tally.js
+++ b/Sprint-2/implement/tally.js
@@ -1,3 +1,12 @@
-function tally() {}
+function tally(myArray) {
+  if (!Array.isArray(myArray)) throw new Error("Invalid input");
+  if (myArray.length === 0) return {};
+  const myObject =Object.create(null);
+  for (const item of myArray) {
+    myObject[item] = (myObject[item] || 0) + 1;
+  }
+  return myObject;
+}
 
 module.exports = tally;
+   console.log(tally(["toString", "toString"]));
\ No newline at end of file
diff --git a/Sprint-2/implement/tally.test.js b/Sprint-2/implement/tally.test.js
index 2ceffa8dd..ebe72898d 100644
--- a/Sprint-2/implement/tally.test.js
+++ b/Sprint-2/implement/tally.test.js
@@ -14,6 +14,21 @@ const tally = require("./tally.js");
  * tally(['a', 'a', 'b', 'c']), target output: { a : 2, b: 1, c: 1 }
  */
 
+describe("tally",()=>{
+   
+    it("returns an object containing the count for each unique item when given array of function",()=>{
+        expect(tally(['a'])).toEqual({a:1}),
+        expect(tally(['a','a','a'])).toEqual({a:3}),
+        expect(tally(['a','a','b','c'])).toEqual({a:2, b:1, c:1})
+    })
+
+    it("returns an empty object for an empty array", () => {
+      expect(tally([])).toEqual({});
+    });
+    it("throw an error for invalid input",()=>{
+        expect(()=>tally("CYF")).toThrow("Invalid input")
+    })
+})
 // Acceptance criteria:
 
 // Given a function called tally
@@ -23,7 +38,7 @@ const tally = require("./tally.js");
 // Given an empty array
 // When passed to tally
 // Then it should return an empty object
-test.todo("tally on an empty array returns an empty object");
+
 
 // Given an array with duplicate items
 // When passed to tally
diff --git a/Sprint-2/interpret/invert.js b/Sprint-2/interpret/invert.js
index bb353fb1f..5e7b229b5 100644
--- a/Sprint-2/interpret/invert.js
+++ b/Sprint-2/interpret/invert.js
@@ -6,24 +6,42 @@
 
 // E.g. invert({x : 10, y : 20}), target output: {"10": "x", "20": "y"}
 
-function invert(obj) {
-  const invertedObj = {};
+// function invert(obj) {
+//   const invertedObj = {};
 
-  for (const [key, value] of Object.entries(obj)) {
-    invertedObj.key = value;
-  }
+//   for (const [key, value] of Object.entries(obj)) {
+//     invertedObj.key = value;
+//   }
 
-  return invertedObj;
-}
+//   return invertedObj;
+// }
+// console.log(invert({a:1, b:2}))
 
 // a) What is the current return value when invert is called with { a : 1 }
+//{key:1}
 
 // b) What is the current return value when invert is called with { a: 1, b: 2 }
+//{key:2}
 
 // c) What is the target return value when invert is called with {a : 1, b: 2}
+// {"1":"a", "2":"b"}
 
 // c) What does Object.entries return? Why is it needed in this program?
+//It turns an object into an array of [key, value] pairs. We need it so we can access the key and value for each pair in the loop.
 
 // d) Explain why the current return value is different from the target output
+// because we use dot notation which sets a property called key that mean we are not using the variable key so it will overwrites the same "key" property each time with a new value
 
 // e) Fix the implementation of invert (and write tests to prove it's fixed!)
+
+function invert(obj) {
+  const invertedObj = {};
+
+  for (const [key, value] of Object.entries(obj)) {
+    invertedObj[value] = key;
+  }
+
+  return invertedObj;
+}
+
+module.exports = invert;
diff --git a/Sprint-2/interpret/invert.test.js b/Sprint-2/interpret/invert.test.js
new file mode 100644
index 000000000..a27d49db0
--- /dev/null
+++ b/Sprint-2/interpret/invert.test.js
@@ -0,0 +1,9 @@
+const invert = require("./invert.js");
+
+test("inverts a two-key object", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({ 1: "a", 2: "b" });
+});
+
+test("inverts a single-key object", () => {
+  expect(invert({ a: 1 })).toEqual({ 1: "a" });
+});