I’m not exactly a lad, but…
I think you need to make yourself a good timetable, and set a goal of what you want to accomplish in that session. This should be as specific as possible, so work out exactly which topic you’re going to do and how you’re going to learn the information, practice it and test yourself, but keep it realistic. Remove distractions like your phone, tv etc. But also plan a reward, so if you work for an hour you get to watch 20 minutes of your favourite tv show or whatever you want to do
Good luck!