Install windows?

I wanted to completely reset my laptop, but unfortunately I got hung up.

Now he can no longer find an operating system.

Can't I just download Windows 10 online, put it on a USB stick and buy a key of some kind for 20 euro and use it to install and activate Windows?

Hope to get a quick reply, thank you very much.

Yes, you can do that with the download and put on a stick. If Windows was already installed before, chances are that you won't even have to buy a new key. Often these are stored in the BIOS so that you don't have to buy a new key just when you reinstall Windows.

Thank you, super helpful!