That should be pretty easy 
- create a star bp -> ?v=t6u0xwNppMA
- create a int variable in your character bp and create the following nodes:
- now in the star bp you will have to increase the value of the int variable -> so from the overlap node you will have to cast to your character bp - then get and set the int variable from the character bp - when the player touches the star it will get the int variable and add a +1 to it
