Broader tyres than approved?

Hello! We have moved our Suzuki Grand Vitara, 20 years edition, V6, built in 2008, to Mongolia. Our tyres are absolutely exchangeable. In the letter of that time it says that we are allowed to drive in Germany 215/70 R16, 225/65 R 17 or 225/60 R18. Which rims we have, unfortunately, I do not know, could not find any lettering, but are still the original rims. There are zzt. however only 235 tires. If it were possible for the safety-wise on the existing rims wehnen? Legally it wouldn’t be a problem and we don’t really care about the look. Since the roads – if they exist – are very bad, the tyres have to endure a lot. Can someone help me? Unfortunately I have no idea… Thank you in advance!