HELP Slow preview of everything in AE when importing projects

HELP ! I have this bug I can't get out of, it's when I import projects into a working project. Its quite slow to import but the worst part is when it's there, everything in AE is not showing up in any comps...nothing is loading, playing and it often take 15 to 20 min until finally everything is working again..
I did import quite a lot of project because I'm always using assets from templates here and there.. but still, it should not be doing this...sometime it's just a shape animation that I import and it's also super slow in the program afterward.. here's a video.
It's a nightmare! I can't get my work done with this.
I have a pretty fast computer Mac Pro, 16 cores, 96 Go RAM, AMD Radeon Pro Vega II Duo 32 Go
And I'm on AE 2021 and always empty the cache