I like to thank all contributing to this forum. My stragecy is first replace the fan into a 9 blade fan with visco, if this does not work enough then I will enlarge the radiator, and the last step could be the bypass system. The fan is installed and the last two days I drove with around 21/22 C and the temp stayed on the highway solid on 82 C, stoplights and uphill was maybe 85 C. Till now it worked and will keep a close eye on this.
Cees