After playing for about 40h I now have massive lag spikes on every memory dump. This does not happen on a new profile until I open the world I regularly play in. It is only then where other worlds have these lag spikes too. This is the log of me being able to open the world (at end of log):
2021-11-17-2.log

After some testing and getting logs I couldn't even start up the world at one time. After about 30mins of Minecraft trying to start up the word I got this crash report:
Crash Report.txt

Thank you for your answer, but that isn't the case. Cranking up the memory just makes Minecraft lag even more.

Maybe I didn't describe the Problem properly:
When creating a new instance and a New World (a) everything runs perfectly. If I now open the world I mentioned in the upper post (b) in this new instance this happens: "Can't keep up! Is the server overloaded? Running 18531ms or 370 ticks behind". Even if I now switch back to the New World (a) no matter if it is a super flat world or not, every entity is lagging and my CPU (Ryzen 7 2700X) has a terrible time spiking at every memory dump:

You seem to run out of memory, try adding more to the game instance.