Views contextual filter on just ONE of the listed contenttypes I'm not sure how I can accomplish this but I hope you can tell me.
I have a view that lists 2 different contenttypes that has different filters.

Now, I want to use a contextual filter on just one of the contenttypes.

Is there any way I can accomplish this?

Best regards,
That really depends on your specific view configuration. Generally speaking, you can add validation (e.g. what content type to accept as contextual filter) and a fallback behavior (e.g. ignore argument vs. show 404), see screenshot. With these instruments you can achieve pretty much.