Seems like you may have a bad hard drive with bad sectors and corrupt data since you have trouble downloading anything/writing new data to your drive. A fresh install may not fully fix the problem and if a fresh install does appear fixes the problem, it will be temporary and the issue will come back after a while as the drive space gets used up.
So try running a chkdsk /r as an administrator/in an elevated command prompt. This will try to recover/repair corrupt data and mark the bad sectors of the hard drive so that data will not be written to the bad parts of the drive again.
chkdsk
If the chkdsk finds the hard drive to be un-repairable, you will need to get a new hard drive and reinstall Windows anyway.
Don’t worry about having to buy Windows again. Microsoft keeps a database with the unique identifier of every computer that has a legitimate copy of Windows installed. So when you reinstall Windows it is automatically activated or if you click, the “activate Windows” button, it will reach out to the Microsoft database, check the unique identifier, then activate Windows. It has been this way since Windows 7.
Be aware that the unique identifier can change if you change multiple components or a major component like the motherboard, etc. thus rendering your Windows activation key/license invalid, and a new license will have to be purchased. Hard drives are excluded from this category so changing it will not affect your Windows license and you should be able to reinstall Windows from the recovery partition or from a “vanilla” ISO download from Microsoft placed on a bootable USB drive without any activation issues.