How is bitter made?

Hi everyone, i wanted to create, alone and at home, a bitter that could satisfy my needs, since the good ones are way too expensive.

The question is: i was reading online how to do that, and it told me to do a process of cold infusion for something like 40 days.

Do i have to keep doing it for 40 days straight? And if so, does that mean i have to keep a stove on for that long? If it’s like that then it’d better to just save up a little and then buy a good bitter directly, since it’d be also made by experts and i would just be experimenting around. Are there other processes that are doable and not too expensive? Or should i give up?

I’m 20 by the way and i’m turning 21 in less than a month, i’m a legal adult where i live so there should be no problems about this post.