Unusual events and notifications

Good afternoon!

I would like to share my concern about somenthing unusual, that happened two days ago.

I started to see "events" on my calendar and started to receive notifications about different things like: "there might be a virus on your phone" or " someone might have hacked your phone and your personal information might be stolen". I have never received this kind of notifications before and I would like to ask what can I do and if there is something to worry about?

Thank you in advance!

Preslava