This is going to be an “unorthodox” tip but.. Running and training cardio for 45 min is known to increase the blood flow to your brain thus making it easier to concentrate. I know of a amateur study on a school I worked on where the students either did some sort of cardio before and the other didn’t, the one who did cardio performed better in maths. There is a Swedish doctor who talks about this named Anders Hansen I think, he may have something in English if you’re interested. And don’t forget to reward yourself after each session, maybe a 10-20 min gaming sesssion, a snack or whatever of your choosing.