I tried playing this for the holiday, but in its current state is just unplayable. From one dev to another I can try and help here. As far as the programming goes I can't really help there cause I cant see the code. But the optimization is horrendous. I suggest going through all your textures files and reducing their maximum in-game size to 1024 x 1024 even 512x512 for small meshes. While 4k looks awesome unless someone has an amazing computer that can handle that many 4k textures being rendered at once it's gonna run like garbage. You really shouldn't be using 4k textures on assets unless its like a character or an Item that will be viewed very close to the player like a weapon or gun. Next, I would check the cull distance on your particle effects and make sure that aren't rendering when the player cant see them. That just wastes processing power. You could do that with meshes as well. I see this was made in Unreal so it should do this for you by default but sometimes when you use pre-bought assets some settings might be different. Last I would look through all your post-processing volumes in your level and on your cameras and disable all motion blur it's really jarring and is not doing you any favors here. I hope you take this as constructive criticism and not as an insult.
Also try and reduce the number of dynamic lights you have in your levels and use static baked shadows where ever possible. If you have a bunch of lights casting dynamic shadows that is really REALLY bad.