I’ve unistalled sket 2018 then instal 2020 but my operating system continues loading 2018 Sket
Did you installed Sketchup 2020 properly? Make sure that no Sketchup is running (you can restart windows to be sure.)
Then right click on the installer file of Sketchup 2020 and chose Run as administrator, then select Repair.
You can also manually re-assign by file type to the right version of SU application if you click on the icon shown in your screenshot…
Tried both things, did’nt help
SketchUp 2019 and 2020 had an issue where you would see duplicates of an older SketchUp (2018 in your case) instead of seeing 2019 or 2020. When you set the application that should open SKP files, one of the entries in the list really is 2018, and the other is 2020. You can pick one of the two and see which version opens when you double-click on a SKP. If 2018 opens, then 2020 is the other 2018 in that list.