Welcome to flying in summer 2022. It's not fun, but you are very far from alone in these troubles, as all media reports can verify. I can empathise with your frustration, but know that the staff are overworked at present, quite a many are actually sick with Covid or in isolation because of exposures - at the end of the day, they are humans as well and deserve to be treated as such. Patience and civility, with a bit of tenacity, will get you more far than anger, in my experiences, and eventually some one will reply to your claim.
File your report and make the appropriate claim (900EUR is certainly within standard coverage, although helping to have a photo/receipt/proof of anything particularly valuable or unusual), as noted by others ping them every few days.