a level physics help

basically with a level physics our classes are split between 2 teachers. one of my teachers is so good and i understand all of the content taught so when i revise its really just refreshing my memory. however the other one is so insanely buns i genuinely don't understand anything we're doing. we just finished waves and every lesson is just him going off-topic and on different tangents. i don't know what to do for all the topics he's teaching because luckily even for gcse my teachers were all decent so i've never had to self teach an entire topic. any advice or help would be appreciated cause i acc don't know what to do if this continues (which it most likely will) for the whole a level. thanks!