For Some reason when I mirror the pot handle this happens. Why?(see image below)

This is because you Rotated the handle in Edit Mode (or Applied the Rotaion) and it is exactly what you should expect; When not spicified, the Mirroring is done around the Origin of the Object:

An exact way of solving this could be:

in Edit Mode, select a Face of the handle and click the + to create a new Orientation:Then in Object Mode go to Options and check Affect Only Origins:

Then go to Object:

And then your Object’s Origin ‘fits’ to your Object again. You might need to adjust the mirroring axis:

Don’t forget to uncheck the Only Origins Option.