After i installed Wireshark in my computer, i saw that the phone was sending a lot of MDNS and DTLS requests (check attached screenshot. My phone has the 192.168.1.156 IP)
Attachment 344379
These protocols are used by all google devices like chromecasts and so on to discover each other. As i don't have any, i tried blocking these protocols from my router but it seems that my router is too dumb to do that :/
I also noticed in my PiHole, that my device is sending a lot of requests to mavenir.com. I have absolutely no clue what is that for. The more info i found was
this article ([only in german)
Still with the denied protocols and that domain blocked in the DNS, i am unable to connect my phone to my WiFi without freezing my router