Do a favor to yourself: Read This

While you learn something, doesn't matter its what. you need to taking note and making a knowledge base for yourself. for this purpose really you need a powerful note taking software its must be cross platform you not always in Linux you not always in Windows and Mac you need to access knowledge base in any OS as well without any stress and also its must be Secure, Free and Open-Source. here is two my favourite software used for long time

1. CherryTree

2. Trilium Notes

Both are best, check out them and use it.

Regards, Hide01 | @Hide01