Editor and game testing is soo laggy

I am using Unreal engine but the problem is that the testing is just laggy.
I made a project and turned it to an excutable but is still laggy.
Sent it to someome else and it still was laggy.
How can I fix this?

That’s a pretty broad one, many things like using lower poly models, lod, draw distance and code optimization can improve performance. Also disable tick on as many actors as possible and make functionality as event driven as possible