Now you can combine several countries in a trip. If you fly through China, and it is convenient to fly through China now, you can stay for 240 hours on a transit visa. Migration Department of the People's Republic of China. List of entry points
Judging by the description from English and Russian sources, you can visit several provinces. That is, make yourself a 10-day tour of China.
Which option is possible, for example:
√ Brussels-Beijing-Xi'an-Shanghai-Hong Kong-Brussels
√ Budapest-Beijing-Xi'an-Shanghai-Budapest
√ Budapest-Beijing-Shanghai-Xi'an-Vietnam
× Budapest-Beijing-Shanghai-Xi'an-Budapest