Dual Monitors help

Sup, I got a new laptop, and when I connect my regular monitor to it, I'm unable to change between only notebook screen/using both screens as extended/only my regular monitor without screwing up all settings.
When I use it on one side or the other, some times it's too bright and some times it's too dark, if I put back regular settings and try using both monitors as extensions, my regular monitor looks great but my laptop screen looks harming bright, really, it hurts.

Any idea on how to keep different settings for different dual monitor options (like it goes, only screen, only monitor, dual or copied)