How can I avoid laggs in Minecraft on servers?

I use Lunatclient for info

Graphics down, render distance down and Minecraft assign more ram are the most effective things how to assign more ram, I don't know with lunar

How am i supposed to whiten it more ram?

As I said, I do not know how it goes brim lunar client must fu googling

https://minecrafthelp.co.uk/how-to-allocate-more-ram-to-minecraft-lunar-client/ I don't use it, but here is a variant

Not at all, just bring something on the local server, not in multiplayer. You can't change lags on third-party servers, this is due to their server or your internet connection.