Where to rent your furnished flat to serious and reliable humans in Berlin?

Hi, I am planning to rent my furnished flat on the west side of Berlin to only really trustworthy and reliable humans who I can trust with my furniture and the peace keeping in the building :) I am terrified by the idea that someone could destroy my belongings and make my neighbors angry.

Do you know really good agencies who vet their clients properly and who take care of all the nitty gritty parts like contract and all? I have to move for about a year for a job offer, possibly longer, but thats not sure yet and cannot afford to pay two rents... I checked out Wunderflats online but their reviews here are scary! Any ideas?