Someone in my system. Remote desktop in and help me, please?

I've had a problem since November 2020. I've wiped my Windows 10 system twice. It's not malware. It's a person on My computer. There are different apps installed that I didn't install. Most notably TechTools Pro. I can't open the app. The icon is grayed out in my Windows/Start menu. I can't remove the app. When I try to access the folders, it says I don't have permission. I need someone to remote into My system and look around. I've hired two techies, and they've both told me it's beyond their ability to deal with. I just disconnected my Windows Live account from My PC, which seems to have solved the issue. MAYBE?. There's at least a key logger on my system because they go thru and change the passwords on my accounts that don't offer 2-factor verification. I've even replaced the Comcast modem to ensure a new IP address. I need to figure out how they are getting into My system to stop it in the future. I'm happy to pay a fee. I have cashapp and paypal.