Building simply disappeared

The game simply made a lot of my buildings disappear. One building's roof is levitating in the air, but the other parts of the building are missing. Random items disappeared, i would say the game reset itself to a previous save, but it did not. Some of my latest building are still (partly) here, but most of them are gone. What should i do? How can i get them back? It is like 4-5 hours of work lost right here

Pls help!!!!