Help With Italian????????

i have no clue whats wrong with me.....last year i took italian i was getting 90s and then i started to go to the 80s then 70s but that was because of laziness....then i got a hard teacher and in the beginning of the year i got 70s and i started to get better by getting in the 80s (69 and below is failing) i mightve failed one or two or three tests this year but otherwise im in the 80s......then i took a practice exam and got almost an 90 and then i took another one right after and i almost passed.....im kinda scared now because i get high or low......when i look up on the computer on help with italian i say to myself i now all of these things.....i dont get it....also im one of the not smartest in the class like the second dumbest.....i dont get it???? like idk if im bad at grammar or vocab and how can i improve in italian?