Some time the windows file explorer takes long time to open and to refresh and it is running slowly in general, Some time the problem is because the Privacy options and the File Explorer history, to fix that :
Right click with the mouse on Quick Access -> options-> at the bottom un-mark the privacy option and click on clear history
Customize Folder Content
You can customize folder content in order to get faster loading time as well :
How to speed up windows folder preformance