tmobile gateway and google nest

I really am not tech savvy at all. I had a hard time finds place for my T-Mobile gateway. I only get a weak signal so I got a google nest WiFi extender. I set it up but I am not seeing improvement. I have read about setting another network or disabling WiFi on the gateway. Have no idea how to do any of this. Can someone give me step by step directions to improve this? Thanks.