so my problem is when i try to play a game on it it will show the nintendo logo and then show a blank screen but if i use a multicart it will show the game list but once i select a game it will just show a blank screen

yes i have cleaned the contacts but with no luck

You may have some debris down in the cartridge slot that is breaking connection. if you have a can of compressed air blast some down in it. Even if you disassemble the unit it is still a pain to get to the connector properly. Usually this is a sign of dirty cart connectors, or either you GB is dying/dead or your carts are one.

Cleaning out the connector very well is your best bet, after that you can go around the board redoing all the solder. If it's still no good it's dead, recycle as parts.