Shenzhen may not be a world's cultural center, but it is, and will be, a world's model of technological advancement. No city in Germany can beat Shenzhen in that aspect.
If you want to define the richness and advancement of a city by its multi-cultureness, then go to any city in Sub-Saharan African or Latin America. These cities are samples of real melting pots, with people of hundreds different skin tones and tribes living together.
And all multi-cultural societies in Europe are dying and cannot be the model of future.