There are multiple things that can be taken into consideration when optimizing a project. First is to just keep your focus on Frame Render Time rather than framerate itself. You can use commands such as Stat unit, stat fps, stat gpu, stat game and profilegpu to get an idea on what is causing the possible bottleneck.
But in some cases, the things that pop up in those commands are too vague to understand and documentation does not help as much. What you can do is to break down your level into smaller parts, and test with turning off (visibility) of some objects and then seeing if it improves the frame rate. Try to make use of Material Instances rather than using materials. Try to make use of Instanced static meshes if you can, download and use Nanite static meshes from Quixel only, if you use Quixel. Rest of the content on it is not made to be performant.
Other things you can look into is lighting, set the attenuation radius properly and try not to overlap. Try fiddling with Indirect light scatter, reflection capture and so. Try exploring settings in Post Process Volume and tweak things in there whether you want to use RT or SS or so on.
Lastly, when you package the game you will have to put in some console commands to set your engine scalability levels using Game User Settings. Make sure to look into that as well.