I don’t really know how to put my problem into words, so I am trying to explain it with an example:
I have a Taxonomy Vocabulary X.
I have Content Type A with Field a, which references Vocabulary X and allows to enter unlimited terms.
I have Content Type B with Field b, which references Vocabulary X and allows to enter unlimited terms.
I want to create View C with a Block Display, which is then placed on a Content of Type B.
How am I going to create a (Contextual) Filter on View C, so that it only shows Content of Type A that shares the same terms like Content B has?