Freezing when deleting a landscape

So I accidently* put some very detailed landscape, when I want to delete them, guess what, it freezes for a couple of minutes* then deletes the landscape, it isnt using cpu nor gpu nor disk for it to be that slow, is there any way to make it faster and not freeze?

Since you deleted a VAST amount of Foliage, there might be no way to do that, maybe alocate more ram to UE, Then you aleardy did?