asset import error UI

I imported an asset on unity 2019.4.0f1. It asked to install package manager dependencies and I confirmed them. Unfortunately it threw a lot errors. ---------- When i uninstalled the 'Package Manager UI' at the package manager, there where no error anymore but also no ui. The publisher of the asset also does not know how to fix it. ---------- Here is a video of the errors: https://www.youtube.com/watch?v=hwr6B74D5ec&feature=youtu.be ---------- Just ask if i forgot some information Thanks for help