struggling with study

hi everyone ! i’m currently a student at a language school in tokyo and i’ve been here studying for about 5 months .
my school is quite intensive and to be completely honest i’m struggling to keep up. We are using みんなの日本語 and we are on the second book at the moment but i am definitely quite behind.
I’m very much struggling with motivation to self study and i’m pretty sure that this is because i just haven’t found a way to study that is effective for me. i really struggle with memorizing vocabulary to be specific.
In January, im supposed to be moving up class to start studying for my N3 however i don’t feel quite ready for that.
With that being said i have roughly 5 weeks until then and i would really like to try really intensively self studying (2-4 hours per day) to try to catch up as best i can before the new semester. if anyone has any tips on different study methods i could try or any advice if you’ve studied minna no nihongo before, it would be greatly appreciated:)
Thank you if you’ve read this far !<3