And finally, I am (but maybe should not be) surprised that no one here
has yet said...

TURN OFF THAT CIRCUIT!

At minimum, you have a loose wire, possibly an open neutral, and
possibly some leakage from hot or neutral to ground, and possibly some
open grounds. At worst you have a potential ground fault somewhere,
just waiting to catch fire, or shock/injure/kill someone when they
touch anything connected to that ground. A whole lot of house fires are
related to electrical problems just like yours.

So go now to the breaker, and turn off that whole circuit. Don't turn
it back on until you (or someone you hire) finds and either (a) fixes
the problem, or (b) disconnects the broken/dangerous portion of the
circuit so you can still use the working portion of the circuit.