I believe I have to load the game again because I put the inverter into the maintenance hatch. Which raised the skeleton. Now I can't get him down anymore because Rufus does not take the inverter out once it's in. All he says is that the skeleton should cooperate with holding the mirror. However I don't think I can get him down again. Yes I looked it up in a walkthrough as I got stuck.

I'm going to load my game again..

Edit: Searched a german walkthrough and I got it fixed. Phew. .