So, the instructions about getting in were unclear, since we were supposed to ring the bell like the host told us, but that was, in reality, the bell to the apartment, so if no people were inside at the time, then you couldn't get in. Thankfully someone from another floor opened the door for us as we waited.
Then, we were supposed to be staying in Room C, and when we went in, someone else was staying there, which was a very awkward experience for both us and them, so we ended up staying at room D instead. The guys staying at room C had encountered the same problem like we did.
Overall, our stay ended up being a rather pleasant one, thanks to the rest of the tenants being very helpful and welcoming in place of our host.