Translation needed for existing languages

[github-actions]

@sumn2u has made changes on the original english version of the book (PR #257)

Visual Diff of Changes:

diff --git a/en/behind-scenes/call-stack.md b/en/behind-scenes/call-stack.md
index 39a392c..f386d99 100644
--- a/en/behind-scenes/call-stack.md
+++ b/en/behind-scenes/call-stack.md
@@ -5,7 +5,7 @@ description: Understanding Call Stacks in JavaScript
 ---
 
 
-## Understanding Call Stacks in JavaScript
+## Call Stacks in JavaScript
 
 In JavaScript, a Call Stack is a data structure that uses the Last-In, First-Out (LIFO) principle to temporarily store and manage function invocation (call).
 
diff --git a/en/behind-scenes/engine.md b/en/behind-scenes/engine.md
index ff9457c..f5d3386 100644
--- a/en/behind-scenes/engine.md
+++ b/en/behind-scenes/engine.md
@@ -4,7 +4,7 @@ pageNumber: 258
 description: Understanding JavaScript Engines and how they execute JavaScript code. 
 ---
 
-## Understanding JavaScript Engines
+## JavaScript Engines
 
 A JavaScript engine is a program or an interpreter that executes JavaScript code. The most well-known JavaScript engines are V8 (used in Google Chrome and Node.js), SpiderMonkey (used in Firefox), and JavaScriptCore (used in Safari).
 
diff --git a/en/behind-scenes/event-loop.md b/en/behind-scenes/event-loop.md
index 2b200d5..b1e1896 100644
--- a/en/behind-scenes/event-loop.md
+++ b/en/behind-scenes/event-loop.md
@@ -4,7 +4,7 @@ pageNumber: 259
 description: Understanding the Event Loop in JavaScript.
 ---
 
-## Understanding the Event Loop in JavaScript
+## Event Loop in JavaScript
 
 The event loop is a fundamental concept in JavaScript that allows for asynchronous programming. It is responsible for executing code, collecting and processing events, and executing queued sub-tasks.
 
diff --git a/en/behind-scenes/execution-context.md b/en/behind-scenes/execution-context.md
index 7523dd2..c40110c 100644
--- a/en/behind-scenes/execution-context.md
+++ b/en/behind-scenes/execution-context.md
@@ -4,7 +4,7 @@ pageNumber: 260
 description: Understanding Execution Context in JavaScript.
 ---
 
-## Understanding Execution Context in JavaScript
+## Execution Context in JavaScript
 
 In JavaScript, an execution context is an environment where the code is evaluated and executed. It is a fundamental concept that helps manage the scope and behavior of variables and functions.
 
diff --git a/en/behind-scenes/memory-heap.md b/en/behind-scenes/memory-heap.md
index b08924d..1033eb0 100644
--- a/en/behind-scenes/memory-heap.md
+++ b/en/behind-scenes/memory-heap.md
@@ -4,7 +4,7 @@ pageNumber: 261
 description: Understanding Memory Heap in JavaScript.
 ---
 
-## Understanding Memory Heap in JavaScript
+## Memory Heap in JavaScript
 
 In JavaScript, memory management is crucial for ensuring efficient and smooth performance of applications. The memory heap is a region in memory where objects, strings, and closures are stored. It is managed by the JavaScript engine's garbage collector.
 
diff --git a/en/behind-scenes/runtime-environment.md b/en/behind-scenes/runtime-environment.md
index eea4ee4..45eed9e 100644
--- a/en/behind-scenes/runtime-environment.md
+++ b/en/behind-scenes/runtime-environment.md
@@ -4,7 +4,7 @@ pageNumber: 262
 description: Understanding Runtime Environment in JavaScript.
 ---
 
-## Understanding Runtime Environment in JavaScript
+## Runtime Environment in JavaScript
 
 The runtime environment in JavaScript is the context in which your code is executed. It includes the JavaScript engine, the call stack, the memory heap, and the APIs provided by the environment (such as the browser or Node.js).