I don’t know what assistant is but to permanently disable updates, all you need to do is follow these steps

1. open windows run by pressing Win+R key
2. type services.msc
3. press enter
4. from the list scroll down to bottom and look for Windows Update
5. Double click on it
6. In Startup type, choose Disable
7. press Apply and then Ok.

And it’s done. Your PC won’t update ever unless you select Manual again from there.