New User Registration on wordpress blog

Hello,

I need some advice with an issue I’ve been facing lately.
I keep getting emails from WordPress about password changes and new user registration on my website. All they say is this:

Password changed for user: wpuser_qbrnuaitibka

or

New user registration on your site Dana Paraschiv | Blog de C?l?torii:

Username: wpuser_qbrnuaitibka

Email: [email protected]

This happens once every few days and I only receive this emails, there is no notification about the contact form or newsletter subscribe being completed.
Is there any way I can stop this? Or is it something dangerous I should look out for?

Thank you so much for your help!

The page I need help with: [log in to see the link]