I see you already have simplify enabled!
Your file doesn’t seem that slow to me!
It does take a little time to compile when you first switch to viewport shading, this is normal.
As Spikey said, reduce the detail in your noise textures on all your materials
Anything above about 5 will not do much or will not even be noticeable.
You could also hide some objects you are not working on.
It may seem faster in the video, but remember the video maybe edited to remove the wait time of viewport shading
