My works got rejected when i spent hours making them what is wrong with it?

Hey ​@Alicia_Lea  These are fun and cool images.
The lock and key for example needs a bit more clean up. 
I would definitely use the Pentool in Illustrator or PS to do the job.

Cheers

Nate
 

Examine at 100% magnification or higher. There are many wonky patches in the lock & key. 

Sloppy mistakes by AI?

You need to do some additional cleaning up. Jagged edges and poor cutouts.