It sounds pretty bad. First option is to run the built-in anti-virus program from Microsoft. It's called Defender and you find it under Settings>Update & security>Windows Defender.
If this doesn't solve your problems, you could consider doing a factory reset using the small Novo button right next to the power jack (on the left side of the computer - it has a small curved arrow). This will bring up a basic menu that allows you to restore the computer to the state when it left the factory.
Please note: This is a drastic measure that will wipe out everything on the computer. If you have important files, you should try and copy them to a USB stick prior to launching a factory reset.
Depending on the computer's original state, you might end up with a different operating system (Windows 7 or 8). If so, it's not the end of the world because you can still install Windows 10.
Cheers,
GreyCatz.