What thing should I learn for encrypting and hacking data and virus and malware functions

For encryption and decryption you can use cryptography module or you can make your own. For viruses and malware you have to make your own functions. I have made RAT which is virus and transfers data to server after encrypting data packets. It have many functions from which you can learn or you can just use it. It is very easy to use. https://github.com/ShailMurtaza/Reverse-Shell