I've read that paprika is good for goldfish and now i'm not sure should I give them fresh paprika or should I boil it first? How can I prepare paprika for GF?

You only need a tiny amount for goldies. Add some to a gel food.

isnt 'fresh' paprika red pepper? paprika is just dried powered red pepper as far as i know????
You can feed red pepper by skinning it and boiling it or steaming it til its soft enough.
alternatively you can add paprika powder to gel food mixtures