Originally posted by guillaume.dequerst666:

Impossible for me and my friends to play on our server due to connexion issue. Same for you ?

Try this:
https://jamesachambers.com/revisiting-fixing-valheim-lag-modifying-send-receive-limits/

Read the page step by step to understand the issue.
Also read the comment section below - there is much additional information.

The problem is hardcoded and can not be solved this way, but you can make it a lot more enjoyable by editing the server .dll or understanding the problem and may make some adjustments to your groups playstyle.

To solve the server lag, the devs have to rewrite the code from the scratch.
To be honest... ever thought that's why Mistlands took so long, but they haven't touched the code since ages.