Hi and bienvenue
The German army Continental LM90 is what I consider a „suicide“ tire - it’s only good on dry / dusty roads - but no go on wet or mud
Actually this tire is the main reason for many damages / accidents in the German Army front end specially- to compensate this poor tire use the light 4x4 but then U will wear transfer quicker - best is to get cooper or BF Goodrich in 235/85/16 even on original steel wheels - you will rev lower - top speed - don’t push it as the Wolf was built to drive in convoy I.e. 80 to 90 km/h.
Ref the preheating, one of the plug or 2 is most probably not working - get the Mercedes ones and not the cheap eBay as U will need to pre heat twice - based on own experience - for services in the car and since U are in France advise U go to the truck / utility van garages as the regular sedan dealer will have serious issues to deal with your requests but again see for yourself
Make sure the visco coupling fan is running and the thermostat is operating properly- give a good clean at the cooling system. Not sure what was done but ensure all oil fluids are changed as the army uses 10w40 oil for almost everything in this car - it’s ok at 70 to 90 km/h but advisable under private use
Enjoy the Wolf is the best every built G!!
Since u are photographer get us pics