A fellow filmmaker in Germany is considering buying a Sennheiser ew112P G4-C but doesn't know if the C frequency range of 734-776 will work in Germany.

Anyone here from Germany who uses wireless lavalier kits know what ranges are good to use ?

I would say yes. https://assets.sennheiser.com/global-downloads/file/9973/ew_100_G4_C_Range_Frequency_Sheet_01_2018.pdf