My cousin and I stayed at Tim and Nicole's place for 3 nights and everything went as smoothly as possible. Just like everyone else said in the comments before us - the cleanliness of the place is impeccable. They have 2 cats in the yard and I got worried that this would affect my allergy but the cats do not go in the place at all, plus the hut was spotless and so well-kept!
Tim and Nicole were very kind and when we arrived they were already waiting for us. They gave us the key, explained everything we needed to know and were nice enough to answer all of our questions (and we had plenty). During the last night of our stay we had a challenging situation and had to contact them. They were very responsive and even came to our place to help. It was such a relief to find that we not only rented a place to stay but also had reliable people to count on in a foreign country!
I recommend Tim and Nicole and if my cousin and I ever visit Berlin, we'd definitely choose their place again.