added a course, a cheatsheet, a tutorial (changes made) (#9846)

* added a course, a cheatsheet, a tutorial

* removed errors

* updated file according to requested changes.

courses/free-courses-en.md

@@ -544,6 +544,8 @@
 * [Practical Deep Learning For Coders taught](http://www.fast.ai) - Jeremy Howard
 * [Practical Deep Learning for Coders, v3 (using fastai library)](https://course.fast.ai)
 * [Self-Paced Courses for Deep Learning](https://developer.nvidia.com/deep-learning-courses)
+* [Stanford CS 224N: Natural Language Processing with Deep Learning](https://www.youtube.com/playlist?list=PLoROMvodv4rOSH4v6133s9LFPRHjEmbmJ) (Stanford Online)
+* [Stanford CS230: Deep Learning](https://www.youtube.com/playlist?list=PLoROMvodv4rOABXSygHTsbvUz4G_YQhOb) (Stanford Online)
 * [Unsupervised Feature Learning and Deep Learning](http://deeplearning.stanford.edu/tutorial)
 * [What is Deep Learning](https://www.udacity.com/course/deep-learning--ud730) (Udacity)
 
@@ -1562,4 +1564,3 @@
 ### YAML
 
 * [Complete YAML Course - Beginner to Advanced for DevOps and more!](https://www.youtube.com/watch?v=IA90BTozdow) - Kunal Kushwaha
-

more/free-programming-cheatsheets.md

@@ -122,6 +122,7 @@
 
 * [Algorithms and Data Structures Cheatsheet](https://algs4.cs.princeton.edu/cheatsheet/)
 * [An Executable Data Structures Cheat Sheet for Interviews](https://algodaily.com/lessons/an-executable-data-structures-cheat-sheet)
+* [Big-O Cheat Sheet](http://bigocheatsheet.com)
 * [Big O Notation Cheat Sheet](https://algodaily.com/lessons/big-o-notation-cheat-sheet)
 * [Data Structures and Algorithms Cheat Sheet - Cheatography](https://cheatography.com/burcuco/cheat-sheets/data-structures-and-algorithms/)
 * [Data structures and algorithms study cheatsheets for coding interviews](https://www.techinterviewhandbook.org/algorithms/study-cheatsheet/)

more/free-programming-interactive-tutorials-en.md

@@ -442,6 +442,7 @@
 * [SQL Tutorial](https://www.w3schools.com/sql) - W3Schools
 * [SQL Tutorial](https://www.scaler.com/topics/sql/) - Scaler Topics
 * [SQLBolt](http://sqlbolt.com)
+* [SQLZoo](https://sqlzoo.net/wiki/SQL_Tutorial)
 
 
 ### XML