Take an opensource project you like and follow its development. Each bug has description and commit that fixes it. If you can reason how bug was fixed, you wil

Take an opensource project you like and follow its development. Each bug has description and commit that fixes it. If you can reason how bug was fixed, you will be good. Also some projects have very good documentation. Read it from start to finish. Do not drink coffe, sleep well, avoid stress.. anything that reduces your cognitive abilities...