Heating + permanently fogged windows

Hi guys, I’m new here. Have two really big problems on board. Have an Omege B 2,5L TD, Caravan. Built: 9/95. 214,000 Tkm down,6cylinder engine. The engine is a BMW engine that is rebuilt. I have a GROßEN LADELUFTKÜHLER,large oil cooler in it. Now to the problems: 1. The heating goes on stage 4 only on lukewarm.With the cold full Sche…. Drive at the time only short distance.After about 10-15 km wierds a bitle warm.Operating temperature is normal 90°C loud. Thermostat is a new inside,ö Opens up to 80°C. Coolant liquid is no good in it. 2. My slices permanently fog all, from forne to back I am at the end with my latain and clenched. I hope you can light me up as soon as possible.My wife is already ready with the noodle wood. Thanks in advance. MFG Sascha