Game goes down to 1 FPS because of render distance.

My project I’ve recently been working on has a lot of polygons, and whenever I look at the whole map it lags my game extremely bad. I’ve tried optimization, but I think it’s because I’m seeing every polygon at once and I can’t change my player’s max viewing distance because it’s grayed out. I also can’t change skeletal mesh’s LOD settings, so it’s very poor frame rate. After watching countless YouTube videos, I still can’t change any LOD settings in my pawn character’s view or my skeletal mesh’s polygons. What do I do?