An upload might be slow for one of two reasons:
1 - Internet connectivity is poor.
In this case, try to find a stronger/faster connection and re-upload your file.
If your router offers a 5G network, switching to it will provide faster bandwidth as long as you are reasonably close to the router.
2 - The file is very large.
In this case, open the file in QuickTime or another video editor and export the file in a smaller size. 1080p (Full HD), or even 720p (Standard HD), will be plenty for most use cases.
If all else fails, upload the videos to Dropbox or Google Drive and email email@example.com for help porting them over to Reduct.