Hello andreaarigo.
Welcome to Apple Support Communities.
If I'm understanding correctly, you recently set up iCloud Photos on your iPhone, however you have some questions about the time it is taking to upload all of your photos to iCloud. You would also like to know if it is okay to disconnect your iPhone from the PC. I will be glad to assist.
The upload of your photos will occur wirelessly, so you are able to disconnect from the computer.
Also, please see the following information below from:
"Your collection uploads to iCloud each time your device connects to Wi-Fi and your battery is charged. When you have iOS 11 or later, your library updates over cellular too. Depending on your Internet speed, the time it takes for you to see your photos and videos on all of your devices and iCloud.com might vary."
When you turn on iCloud Photos, the time it takes for your photos and videos to upload to iCloud depends on the size of your collection and your Internet speed. If you have a large collection of photos and videos, your upload might take more time than usual. You can see the status and pause the upload for one day."
Cheers.