If you are experiencing slow in uploading videos in your store then try the below-mentioned process:
First, check your uploading speed by using this Link
During the upload, do not put anything in the descriptions; no tags, unmonetized, no thumbnail and just put one single letter on the title. The video will upload faster because it doesn't have any additional information to process.
Delete cookies, offline files of your browser. Always use an updated browser.
If you are uploading from your desktop, then you need to make sure the connection is uninterrupted. i.e. your computer is on and browser open the whole time (don't let it go to sleep). Don't even refresh the browser during uploading your video.
If you are still experiencing issues while uploading your videos, then you can try uploading videos via FTP.
While uploading videos via FTP, you don't need to watch your browser constantly to view uploading status as the uploading occurs in the background.