[betgo]

I hope it is OK to reply in English. I can read German better than I can write it.

A larger raise preflop is standard, particularly OOP and with AK.

The check on the flop is not terrible. There is a middle card and a 2-flush, so it may not be easy to get villain to fold. Since you reraised small preflop, it is probably better to cbet about 20, continuing to represent an overpair.

I would never think of checkraising the turn. There are some advantages to this line to pressure flush draws. I think you need to just bet out on the turn. Once you check, you could also just flat call the small bet.