i took my pc to a shop to install the parts and asked them to install windows 10 turns out they installed a counterfeit version for free thats why if ur asking
ABDULITY: If you buy a license, it will not cause you to lose your programs during the activation process. All activation does is registers the license (product key) on Microsoft's server and it's a process that is not even visible to you, except at the end it should say your Windows is activated.
You should be able to simply insert the key from the retail version under Settings > Update & Security > Activation. There's an option to change product key.
Microsoft allowed free Windows 10 upgrade for a certain time frame. Maybe you were within that time frame. It it wasn't legit, you would know it because MS stops updating and give you nasty messages.
It was basically your fault for taking your PC to them, I think you should've taken the time to construct a search on that shop before you went there. Remember this as a lesson.
Just as "Steve S" said, I'd recommend just reinstalling it from scratch. It's not really known what could have come with that hacked version, even if the person who worked on your computer is trustworthy.
Id back up and reinstall who knows what trojans and back doors are in a hacked version.