Take a real compsci intro course, one that teaches 'systems engineering' as in what a testing oracle is
https://learnaifromscratch.github.io/software.htmlThen you pick up books or read papers on google scholar about whatever protocol you want to work with
Then you can either do gitcoin bounty's and write features in excange for coins or you find some open source wallet or whatever and get your PRs approved
Get a few PRs accepted and maybe somebody will look at you, or enter via customer support on one of the big exchanges and weasel your way into development internally
If you want to take a real cryptography course from dj bernstein's gf then here you go:
https://functionalcs.github.io/curriculum/#org92df451 it assumes you know linear algebra