inventories and enemies, i need help!

im up to making inventories and enemys, any sugestions and/or code? (this is for the action rpg platformer)

i also need a way to go to the previos level

heres the game so far https://microstudio.io/coolbananagames/meowys_adventure/neozon123vbnas/

make the code public and post a link to the project .