Biting Problem, PLEASE HELP!

Does anyone know what this noise means? I’m sitting in the bathtub and letting her crawl around and I gave her a treat too, is this a good thing? My hamster is a dwarf hamster btw if that helps! Audio is very quiet so you’ll have to turn it up, it’s this tiny chirping sound

This is Mimi’s new set up! I’m currently too broke to buy more bedding so this will have to do for now, but I took everyone’s advice and I got her lots of hiding spaces(the wheel I ordered was too small in getting a replacement I just kept it for the photo, also toys added after picture)

THANK YOU FOR THE TIPS!

Why is my hamster climbing her cage when I walk over to take her out, and when I put her back in?

Please help!