We felt really welcomed at Jang and Christian's. They gave us a map and some information about Oslo.
They advised us about the things to see and how to get there with public transport. Thanks to this advice, we went to Oslo islands without the touristic cruise and it was a really nice journey.
Their flat is very clean and tidy, very well located in a nice and modern neighborhood, near the sea and art galleries. It's a few minutes away by foot from the city center and near public transport.
Jang is a really good cooker ! She cooked us a delicious Thai dish: red ruby fish. Don't hesitate to ask her the menu ;)
To put it in a nutshell, we spent a really nice weekend at Christian and Jang's and we recommend their place to stay in Oslo.