How can i mask several layers without masking seperately?

Effects have a Mask Reference feature which allows you to have an effect work within one or more Masks.

More info here - https://helpx.adobe.com/after-effects/using/mask-reference.html

You cannot exclude layers from adjustments when they are below in the stack. You have to restructure your project by separating the individual layer sets in pre-compositions. I suggest you actualyl read the online help on such basics.

Mylenium

You can write several masks on one adjustment layer. You can also have the adjustment layer only above the layers that you want the masks applied to in the timeline. I'm not sure I understand your question but I hope that this helps.