Hi! I recently bought my first bonsai. It 5 years old. It awoke from winter time and have little leafs already. But I want to prune some brunches. Can I do it or I should wait until next spring?

I would probably wait a bit untill it has finished this flush of foliage. Then end of may defoliate, trim, wire.

Also I’m thinking about repotting it in a bigger pot to make it grow lil faster. To make its trunk thick. Will it work?

Anastasia wrote:

Also I’m thinking about repotting.To make its trunk thick. Will it work?

Yes.
Better in the ground, but a bigger pot or a colander will help.

If your aim is to grow the trunk you should trim as little as possible. You will need all the leaves that you can grow.