HELP!!!! new to programming

i have made this platform game for one of my college assigments but it has a load of issue i'm stuck with

first issue if you play the game u see u have to get coins to make the red box apper to jump to next level but i have only hidden the box so u can just go jump on without getting the coins anyway round this

also i have problems with my closiion when i jump onto platfroms angles i wil fall right though for example on level one if i jump at an angle the charter will fall though the screen.

also anyyone know where i can get more help to make a side scrolling platfrom ??????