an international transfer, is it possible to leave the Guangzhou airport for only a few hours?

In November me and my girlfriend will be traveling from Hanoi (Vietnam) back home in Europe.
On the way we will have a stop at the Guangzhou Baiyun International Airport.
We arrive at 19.00 hours and depart 23.55 hours (4 hours and 55 minutes)
I was wondering if you could help me by answering the following questions:

- Is there a possibility to have a short sleep in a nearby hotel?
- Do we need to leave the airport / pass the customs and do we need a visa if we want to stay at the hotel?
- Is it possible to leave the airport for a few hours and visit Guangzhou?
- If possible, do we need a visa if we want to visit Guangzhou for only a few hours (and what kind of Visa)?
- Do you have any other suggestions to spend our time while waiting for our connection flight?

Hoping that you are able to answer the above questions and hoping to hear from you