Hi again NourinE
It's not too unusual for Windows 10 to startup slowly if a lot of updates are being installed. Sometimes the blank screen is due to the files getting sent to where they need to go. Since you've just upgraded, you are likely to have quite a few updates available -- these will make your system startup quite a bit slower. But this should resolve over a few days, and then things should start up faster.
If the normal login screen doesn't display, even after waiting for up to 30 minutes, you can try a Startup Repair. Here's how:
Windows 10 Startup Repair
1) Click on the Windows Start Menu icon
2) Select Settings
3) Select Update & Security
4) Select Recovery
5) Select Advanced Startup
6) Select Restart Now
7) .... you'll see a "Please wait ..." screen for a moment ....
8) From the Choose an Option screen, select Troubleshoot
9) Select Advanced Options
10) Select Startup Repair
Should that not help, try looking in on your Event Viewer error logs.
1) Right-click the Windows 10 Start Menu icon
2) Select Event Viewer
3) In the left-hand pane, select Event Viewer (Local)
4) For more room to view the errors, click on the up-facing arrows in the title bars for "Recently Viewed Nodes" & "Log Summary" (this will collapse their view ... it's a toggle switch)
5) Look through the errors in the "Summary of Administrative Events" window - and see if any correspond with the same time that your system fails to display the desktop at startup.
Let us know if this doesn't help, or if you have questions.
