shadows causing lag in level?

So I’ve made a level whereby I thought that maybe the number of actors attached to the meshes were causing performance issues. I have everything in engine scalability set on on epic except shadow because everytime i turn them up I get a massive fps drop here on my PC and at uni on their PC’s.

Old screenshot but the only thing not present is the water the scene has everything else you see present.

So yeah my question is why are the shadows affecting the performance soo much?

I do not have a fully technical explanation to this but it seem unreal engine shadow maps are very inefficient when it comes to performance i don’t have any other game engines to compare to but i atleast know that blenders realtime shadows does not affect performance in any noticeable way unless you go over 4096 in shadowmap resolution, what you can do is use distance field shadows as they are less power hungry and you might get not get any extreme lag from shadows anymore, can you tell me how many light sources you have in your level and if they are set to static stationary or movable i also need to know the shadow resolution and if you used any baked lighting.