landscape

hi, i have a question maybe its basic cuz im new to unreal engine.
well i wanna create a landscape but not in original size i wanna make it smaller like 10% of the original size but when i do it in landscape mode and then create the landscape (8k) itll give me massive framedrop when i move camera like from 120 to 20 fps and when i scale it back to 100% itll be fine again and give me 120 fps.
is there a way to fix this?