Extrem lags (can barely move) in certain area of my world

Hello I hope you can help me.

Im running a little server for me and a friend over tunngle (like Hamachi).

I never had problems with the server until yesterday.
When I enter a specific area (multiple chunks) in my world, the game starts freezing and lagging hard and its nearly impossible to move.
I tried different suggested solutions already but nothing worked.
I destroyed the stuff I build up last. I searched for areas with mass spawns, I downloaded MC edit and tried to repair, delete and regenate the chunks, but nothing worked.

I hope you can help me.
Pls tell me which informations you need.