How to actually listen & understand what the teacher is saying during class?

I mostly get good grades in school, however, I mostly have to teach everything myself (especially in scientific subjects, but i honestly have this problem in every subject) because i either didnt understand what the teacher is teaching at all or i wasnt even really listening in the very first place (i hear that the teacher is talking but my mind is somewhere completely different)

It‘s not that I am distracted with anything (like playing games or doodling), I actually try to listen but i feel like the more i concentrate the less information does my brain catch up.

If you had the same problem, how did you overcome it?

Some infos, that might be important:

im a highschool student

we mostly use iPads during class

we students are expected to contribute in class as much as possible