get my iPhone 11 back to my icloud account after someone put their gmail account on my phone and i no longer talk to that person

Tmobile can only help with phone activations and issues with connecting to the Tmobile cellular network. Since you don't mention either of these issues and your problem seems to be within your iPhone, you will get much better service contacting Apple support.

Trust me, the last place you want to call on how to use your iPhone’s functions is TMobile.