For some reasons, I can't start my job or officially work for next 1-2 months.
I want to learn new things, build, but I can't figure it out on my own.
Can someone please advise what's the best way to use my time and not go crazy?
[reposting an old comment]
Which open source projects are you using and you like? Try to contribute to them.
Start sending bug reports that are very useful and sometimes underestimated. Look how/where they fix them and the next time try to send a pull request (or another bug report).
Fixing typos in docs is also a good starting point.
If you want to send a new feature, start with something small, like a weekend project. You never know if the maintainer will like it, or if they are morons or if they have very weird code rules.
That being said - perhaps disconnecting fully from technology may be refreshing. Could work on some other routines like learning certain recipes that may support more sustainable hardworking lifestyle once it resumes.