My house trailer lost power to 2 rooms and some outlets only on one side of my trailer

Try this first go to breaker panel and see if any breakers are tripped off

Also in your bathrooms they should have ground fault outlets. Check to see if its tripped. Its unlikely that's the problem because you saying almost half your trailer is out.

They are all on and the gfb is in good working order I am puzzled

they are all on and the gfb is in good working order i am puzzled

It could be bad breaker but its unlikely 2 are 3 breakers go bad at same time. How old is trailer?