Why was then possible to send my btc if I can't receive it?
Because the Bitcoin Cash developers did not change the address format when they forked the chain there is no way to prevent mistakes like this.
Thats for me a lot of money. And where are my coins then if they are not on that bch adress? Thank you for your answers and I would really appreciate if someone could help me about my problem.
This
Your coins are inside of BTC address. If you dont have private key of that address you cannot access them.
The both wallets are mine and I am sure I have all those informations you mentioned, if that can even help me. Is there any option to retrieve my coins?
As above, you need the private key to the BTC address you sent the coins to. Without that nobody can help you.