Thank you for the quick response Martijn!
Unfortunately I am not hosting the WP Page myself and getting back to my friend hosting it, as it seems the memory-limit is fixed at 128MB or we haven‘t found out yet to change it anyways.
Interestingly the above mentioned error is only thrown shortly after I updated the page in WP. After that I don‘t get any error but just a map without any tracks and any error.
Thus only simplifying remains. I will look into it. I have only an iPad on my travels, let‘s see if I can find a workaround.
Ultimately I could split the total overview to countries or so in order to reduce the total number of point, but as the total has a catch I‘ll follow the simplifying approach some more.
Thanks for the assistance and hints and best regards,
Viktor