Having major superimpose problems!!

[rich2005]

Following on, more information really needed. However, reading between the lines maybe the background(s) are complicated and a simple fuzzy select or c2a is not effective.

Back to basics, Using the Foreground Select tool to get a selection and a layer mask for a tidy up.

Example: duration 4 minutes https://youtu.be/m9_Mz2VbSjA

Yes, editing can be tedious but often necessary.