Transit Visa from Germany Düsseldorf to beijing and than to Bangkok

My GF and I are travelling with Emirates from Düsseldorf-Germany over Dubai to Beijing. Dubai is just a stop-over. We arrive at the 16th November 2:45pm and leave Beijing at the 19th November 03:45am to Bangkok. Flights are booked and our Passports are Valid.
So we are less than 72hours in Beijing.

Do we need to do something in advance for the transit?
Do we need to inform Emirates, that we dont get problems in Dubai?
Do we need to register at the police station, because we will stay at a friends house. (We have an invitation letter from our friend)

Thanks and Best
Björn