While updating Skype would be the most obvious step (and consequently one which genious me had never thought off, so thank you very much for the advise
) it sadly didn't fix the problem.
I got a new Skype account called Malte27984 (less unwieldy names being taken already) and I am just beginning to realize how messed up everything is.
For months I have been wondering why hardly any of my contacts were online anymore or reacted to my posts.