README: Improve cheat sheet copy + add images

README.md

@@ -8,36 +8,66 @@
 
 Source code for the HappyCoders.eu article series on pathfinding algorithms:
 
-## English Articles
+
+## <br>English Articles
 
 * Part 1: [Shortest Path Algorithm (With Java Examples)](https://www.happycoders.eu/algorithms/shortest-path-algorithm-java/)
 * Part 2: [Dijkstra’s Algorithm (With Java Examples)](https://www.happycoders.eu/algorithms/dijkstras-algorithm-java/)
 * Part 3: [A* Search Algorithm (With Java Examples)](https://www.happycoders.eu/algorithms/a-star-algorithm-java/)
 * Part 4: [Bellman-Ford Algorithm (With Java Examples)](https://www.happycoders.eu/algorithms/bellman-ford-algorithm-java/)
 * Part 5: [Floyd-Warshall Algorithm (With Java Examples)](https://www.happycoders.eu/algorithms/floyd-warshall-algorithm-java/)
 
-## German Articles
+
+## <br>German Articles
 
 * Teil 1: [Shortest Path Problem (Kürzeste-Wege-Problem)](https://www.happycoders.eu/de/algorithmen/shortest-path-problem-java/)
 * Teil 2: [Dijkstra-Algorithmus (mit Java-Beispiel)](https://www.happycoders.eu/de/algorithmen/dijkstra-algorithmus-java/)
 * Teil 3: [A*-Algorithmus (mit Java-Beispiel)](https://www.happycoders.eu/de/algorithmen/a-stern-algorithmus-java/)
 * Teil 4: [Bellman-Ford-Algorithmus (mit Java-Beispiel)](https://www.happycoders.eu/de/algorithmen/bellman-ford-algorithmus-java/)
 * Teil 5: [Floyd-Warshall-Algorithmus (mit Java-Beispiel)](https://www.happycoders.eu/de/algorithmen/floyd-warshall-algorithmus-java/)
 
-## The Big O Cheat Sheet
-👉 Use [this FREE 1-page PDF cheat sheet](https://www.happycoders.eu/big-o-cheat-sheet/) as a reference to quickly look up the 7 most important time complexity classes (with descriptions + examples).
 
-➤ [Hier geht's zur deutschen Version des PDFs](https://www.happycoders.eu/de/o-notation-cheat-sheet/)
+## <br>The Big O Cheat Sheet
+
+With this [1-page PDF cheat sheet](https://www.happycoders.eu/big-o-cheat-sheet/), you'll always have the **7 most important complexity classes** at a glance.
+
+[<img src="/img/big-o-cheat-sheet-pdf-en-transp_936.png" alt="Big O PDF Cheat Sheet Mockup" style="width: 468px; max-width: 100%;">](https://www.happycoders.eu/big-o-cheat-sheet/)
+
+* **Always choose the most efficient data structures** and thus increase the performance of your applications.
+* **Be prepared for technical interviews** and confidently present your algorithm knowledge.
+* **Become a sought-after problem solver** and be known for systematically tackling complex problems.
+
+👉 [Download the Big O Cheat Sheet](https://www.happycoders.eu/big-o-cheat-sheet/)<br>
+
+_(Hier geht's zur deutschen Version &rarr; [O-Notation Cheat Sheet](https://www.happycoders.eu/de/o-notation-cheat-sheet/))_
+
+
+## <br>Java Versions PDF Cheat Sheet
 
-## Java Versions PDF Cheat Sheet
-👉 Save time and effort with this [compact overview of all new Java features](https://www.happycoders.eu/java-versions/) from the latest version back to Java 10. 
+**Stay up-to-date** with the latest Java features with [this PDF Cheat Sheet](https://www.happycoders.eu/java-versions/)!
 
-In this practical and exclusive collection, you‘ll find the most important updates of each Java version summarized on one page each.
+[<img src="/img/Java_Versions_PDF_Cheat_Sheet_Mockup_936.png" alt="Java Versions PDF Cheat Sheet Mockup" style="width: 468px; max-width: 100%;">](https://www.happycoders.eu/java-versions/)
 
-➤ [Hier geht's zur deutschen Version des PDFs](https://www.happycoders.eu/de/java-versionen/)
+* Avoid lengthy research with this **concise overview of all Java versions up to Java 23**.
+* **Discover the innovative features** of each new Java version, summarized on a single page.
+* **Impress your team** with your up-to-date knowledge of the latest Java version.
 
-## HappyCoders Newsletter
+👉 [Download the Java Versions PDF](https://www.happycoders.eu/java-versions/)<br>
+
+_(Hier geht's zur deutschen Version &rarr; [Java-Versionen PDF](https://www.happycoders.eu/de/java-versionen/))_
+
+
+## <br>HappyCoders Newsletter
 👉 Want to level up your Java skills? 
 Sign up for the [HappyCoders newsletter](http://www.happycoders.eu/newsletter/) and get regular tips on programming, algorithms, and data structures!
 
-➤ [Hier geht's zum deutschen Newsletter](https://www.happycoders.eu/de/newsletter/)
+_(Hier geht's zur deutschen Version &rarr; [HappyCoders-Newsletter deutsch](https://www.happycoders.eu/de/newsletter/))_
+
+
+## <br>🇩🇪 An alle Java-Programmierer, die durch fundierte Kenntnisse über Datenstrukturen besseren Code schreiben wollen
+
+Trage dich jetzt auf die [Warteliste](https://www.happycoders.eu/de/mastering-data-structures-warteliste/) von „Mastering Data Structures in Java“ ein, und erhalte das beste Angebot!
+
+[<img src="/img/mastering-data-structures-product-mockup-cropped-1600.png" alt="Mastering Data Structures Mockup" style="width: 640px; max-width: 100%;">](https://www.happycoders.eu/)
+
+👉 [Zur Warteliste](https://www.happycoders.eu/de/mastering-data-structures-warteliste/)