You’ll need access to a better (faster) network connection here, or access to another Mac to build a bootable installer. These downloads are big, and can take hours on a slower link, or longer.
A Microsoft Windows system will not be helpful for building a recovery installer.
You’re also on a Mac that’s old enough that the underlying problem here may be a failing hard disk drive, or similar hardware issue.
Hardware Test can potentially show a failing hard disk drive, or other hardware issue.
As a workaround pending repair or replacement, installing macOS onto or restoring your backup onto an external scratch storage device and booting that can be workable. Do you have backups, amd do you have a scratch external storage device?
Failing hard disk drives show as lowered performance, beachballs (system wait cursor), and hangs, and app and system crashes and corruptions.