That's just great but I have no idea how to use it anyway. Cryptopia needs some 'message' and there's no manual on how to add that message as if we all are Linux gurus to figure it out all by ourselves. And this one costs a lot so I don't wanna lose the transaction in case I sign it wrong

I guess i need to choose 'Sign message' then click on 'Sign message' and there's no OK, only 'verify' 'dismiss' or X

we need a manual for the wallet! We never need a manual for any QT wallets out there right? We don't need manuals for Monero wallet either... but THIS...
We are not like any coin out there, Monero or anything else.
To sign a message just fill the "Data" field with the message provided by the cryptopia wallet and that's it.
P.S. To not make this "cost you a lot", first send a test amount of 2-3 coins and see if you get them into your wallet. This is recommended when you send any coin out there, before you move large amounts of money.