Rocket League is not in other games?

As above it is in Rocket League (pc) but if I e.g. Minecraft games run smoothly.
(Internet lag)
I look forward to everyone who tries to help me.

Uff, there can be several reasons.

Are both games running locally?
Do you both play offline?
What components are installed in your PC? In general, Minecraft is not a good comparison because it can save a lot of resources.
Did you ever turn down the RocketLeague settings?

(internet lags)

play online.

Minecraft too?

Yes

https://downdetector.com/status/rocket-league/

If you look at it RocketLeague just seems to have server problems. You won't be able to do much about that