I played Toribash for 3 Months, without every Lag.
But now I installed it new, and now it lags.
I got no Idea why.
Please help me.

reinstalle it

Probably because your computer cannot run new effects such as flames and new graphics options. Mess around with the graphical options in Options and see if you can make it run better.

I dont have new Effects I played Toribash 3.8.
I just had to install it new.

Its said before that the new versions are more laggy.

If your referring to lag when online it'll be down to the servers.

If it's the game running slow/jerky then there's a few things you can try to speed things up.

If you're running shaders then try turning a few of the extra options off.

In options you can set the game to run at either 30 or 60 FPS, setting it to 30 will make it run better.
Flames can cause slowdown, so turning them off with /opt particles 0 will stop them slowing things.
Other things like trails etc can be turned off (/opt trails 0) and depending on your machine you could see a boost.

Not having things running in the background is a no-brainer, Toribash is very processor dependant so the more you let it eat the better it'll run.