This is a list of resources and challenges to learn and practice your reverse engineering skills for CTF's.
Presentation can be found here
Link
Some list of writeups for you to enjoy.
Very Simple .Net Crackme
Beating a trial on a .net crackme using dnSpy
Is it a Flag?
Morty's Sherlocked Writeup
.NET
http://crackmes.one/crackme/5ab77f6433c5d40ad448cb21
http://crackmes.one/crackme/5ca5c1ac33c5d4419da556de
http://crackmes.one/crackme/5ab77f6633c5d40ad448cc4b
python
http://crackmes.one/crackme/5ab77f5933c5d40ad448c43d
https://github.com/IIT-BHU-CyberSec/Technex-CTF-2021/blob/main/rev/marshal/2test.py
(Hint : python version 3.6.9 was used)
java
http://crackmes.one/crackme/5ab77f5333c5d40ad448c0d9
http://crackmes.one/crackme/5ab77f5e33c5d40ad448c794
http://crackmes.one/crackme/5ab77f5f33c5d40ad448c7f8
apk
https://ctflearn.com/challenge/962
https://github.com/lucideus-repo/cybergym/tree/master/cybergym1/mobile