Virus & threat protection showing at load up on Windows Defender

[Heathsideboy]

Just recently, when my computer loads up, Windows Defender is shown on the taskbar with a yellow triangle with an exclamation mark on it. I click on Defender, then under the 'Virus & threat protection' it is telling me to set up OneDrive for file recovery options in case of a ransomware attack.

I click on the button that says, 'Set up OneDrive,' type my email address in. It is then telling me, 'you are already syncing a personal OneDrive on this computer. Unlink that account to add a new one.'

What should I do here & how do I go about this?

Also, often when my computer is loading up, I get a message saying,

'Virus & threat protection,'

'Un-authorised changes blocked'

and then it tells me the path to where the programme is that it is being blocked.

I have never, ever had this come up on my computer before so I am assuming that this has been added to a recent Windows update of some sort.

Is there any way that I can stop this coming up and are all these things I have mentioned above linked in some way?

Thanks

HB