Big Landscape Optimization Tips Needed

Hello, I made a rather big landscape for my game. When you are at one of the ends of the landscape, if you look the far end with your mouse movements, FPS drops so much. Game itself does not have much foliage or lights or anything. It’s just big and I can’t reduce the size of it now. All I want is some optimization ways such as limiting rendering or etc. If there are some settings in World Settings or Project Settings it would be so helpful. By the way, Level Streaming seems so complicated and actually the landscape is not ‘that’ big for setting a Level Streaming system. And Cull Distance Volume doesn’t work the way I want. It only hides foliages as a whole. Long story short, game has optimization problems while looking the far end of the landscape. Basically FPS only drops when you move your mouse and look away. I would love your suggestions for this exact cause.