I've had a few study buddies, all with ADHD. One I knew IRL, the others were from the adhd subreddit.

When you say keep focus for more than 2 days, do you mean you are working on the same thing for that whole time? I do better when I do work on one thing at a time, because starting is the hardest part for me. Momentum helps. But for others, they get bored really easily. If you are like that, maybe you could try switching back and forth between a few tasks? Or working for really short, timed periods, then taking short breaks?

Don't give up!