About Japanese parents and hospitality.

I'm going to visit my Japanese girlfriend, who I met during my language courses in Australia, this summer for two weeks. I offered to book a hostel for the time I stay in Japan, however her parents insisted upon living at their house. I'm quite surprised that they are so generous because firstly, they don't know me (only from pictures, my girlfriend and I have been together since the third week I landed in Australia) and secondly, I almost only read that it is unusual for Japanese people to invite a stranger for two weeks into their house. Don't get me wrong I'm really happy to live with them during my vacation, having a view in a typical Japanese lifestyle and getting to know them, but still it seems strange to me.

• Is it now days more common to have strangers/guests/boyfriends of their daughter for a certain time living with the howl family together (note, I don't have to pay anything - I even asked several times if I can but her parents said that they don't want to) for free? When I told my girlfriend that it seems strange to me and I'm not feeling very comfortable about it, especially with not paying anything, (because I read a lot about that it ISN'T normal, also on this website) she meant that her parents are very open-minded and not as old fashioned as other families are.

• Should I try to speak a little bit Japanese with them or would it be rude, because I'm not very good in it?

• What tips can you give me for living in a Japanese household with Japanese people; I don't want to put my foot in some no goes.

• Should I spend some extra attention on my behavior when I'm near her parents (e.g. be extra polite…)?

• How should I greet them when I meet them for the first time?

• The presents I take with me, give it to them straight away or waiting a little bit?

I'm sorry for my questions and I know I could also ask my girlfriend, but I want to get to know this stuff on my own, so that I can surprise her with my knowledge and good behavior. At the moment I'm reading a book about Japanese culture, but it doesn’t give any good information about daily things so I'm hoping to get some practical advices here (and yes I already read the other topics with similar contents).

Thank you very much for your help and have a nice weekend.
Greetings from Switzerland

How old is your girlfriend? If she is getting close to 30, they might be thinking of you as son in law material.
You will probably feel uncomfortable staying with them, but that is for you to decide.
yes, try to speak Japanese there.
My sister in law is married to a Swiss guy. My in laws love him because he is nice. I'm sure you are too, so things will be fine.

I am a Japanese who has an American husband. When he came to Japan for the first time, my parents let him stay with us (I used to live with them then),and it was also like 2 weeks. The reason that my parents let him stay was because he was a student,so my parents didn't want him to spend extra money for a hotel, and also because my parents thought it was a good opportunity for him to learn or have an idea what Japanese culture is like.
Yes, it would be always better if you can say something in Japanese, but i don't think they expect you to say anything in particular. its not rude at all even if you can't in my opinion.
When my husband met my parents for the first time, he bowed, which surprised me. If you could say something like "hajimemashite" which means "nice to meet you," that would be nice.
You may want to try to help her family like washsing dishes when you can. And smile!