@Sebi07 , Please try to set your modem to factory settings. Gently press the reset button on the back with a needle for about 30 seconds. After the modem is online again, you can try again.
edited on 12-12-2019 20:26
Did you try 27015 instead of 27015-27015?
Can you try other ports? Like port 80? Or 8080?
Is the IP correct? Is it static?
According to https://portforward.com/ark-survival-evolved/ you have to forward only 27015 for TCP and not UDP but you selected "Both". Choose TCP only.