@Pablo1234 How many people the room could hypothetically accommodate two people is completely irrelevant here. What matters is how many guests you registered in your original booking. If you reserved as a party of 1, your host accepted you and only you as his guest. That agreement does not extend to any additional people you might want to bring into the flat for any length of time, as a casual visitor or overnight guest. It's entirely at the host's discretion whether he chooses to allow any people he didn't personally approve into his own home, and it would be incredibly disrespectful and presumptuous to simply bring another person into his residence without his explicit permission.
In other words, it's not the host's duty to tell you you can't bring other people into his own flat - it's your responsibility to ask.
If your original intention for this rental was to share it for any portion of the time with your girlfriend, you should have either booked and paid as a party of two, or asked about overnight visitors in your original request. If you failed to do that, then there's no reason Airbnb would grant you any kind of refund, because the host has done absolutely nothing wrong. However, if you submit a booking change request and ask to shorten your stay, you might be able to reach an agreement with the host for a partial refund of your unused nights. Once again, that's entirely at the host's discretion - there's no reason he should be losing out on income just because you wanted to sleep with your girlfriend.
