One small problem! tile based game help

Hi everyone! I’m making a game. it uses an 2darray to store the tiles, it doesn’t scroll it’s like uhm …the old donkey kong! and its my first game like this! everything is working fine. but when ever you win and load up a new level the game runs a little bit slower. until finally you reach around level 12 or so and it’s totally bogged down lagging and oh man.
so how would i build in the new level into the array with out holding all of the old like memory into the computer? do you guys see what i’m trying to say?!! i’m at work so i can’t give you any files but i was jsut wondering how you clear out the memory from an old array. i’m pretty sure thats the problem. now i jsut have the level. and when you win it takes the same array called level and then replaces the tiles in there… AHH sorry if i’m confusing you guys i just really want to figure this out! do you guys even think this is the problem?! thank you so much for any insight on fixing the issue!