Performance issues when working with large terrain

Hi all! I encountered some crazy problems when creating a large landscape. I want to create mountains around a large airfield - 2.5 kilometers long. What parameters should I choose when creating a landscape so that the engine doesn’t slow down? Now it takes half an hour to process the creation and deletion of each segment. Landmass can barely move. It is impossible to work at such speed. My computer is very powerful. What is wrong with me, I will be grateful for any help)

Its what is wrong with the engine, not you.

Use meshes. Not the landscape.