Thank you for sharing this.

Anyone would recommend resources for learning fundamental of data structures?

Book, video, or courses are welcome. I don't care the programming languages that are used for implementations. I am OK with C.

If you are interested in Video lectures, there are plenty of resources available at this link: https://github.com/Developer-Y/cs-video-courses

For data structures in specific, You can go through following courses

1. CS 61B, Prof Jonathan Shewchuk, UC Berkeley -> [1]

2. COP 3530 Data Structures and Algorithms, Prof Sahni, UFL -> [2], videos are available at [3]

3. COP 5536 Advanced Data Structures, Prof Sahni - UFL [4]

All above courses focus on ideas than on mathematical rigour.

[1] https://www.youtube.com/playlist?list=PL4BBB74C7D2A1049C

[2] http://www.cise.ufl.edu/~sahni/cop3530/

[3] http://www.cise.ufl.edu/academics/courses/preview/cop3530sah...

[4] http://www.cise.ufl.edu/~sahni/cop5536/index.html