404 monitor doubts

Hi guys,
I cannot understand why I have so many 404 urls.
How is it possible that, in the list, there are the two homepages (italian and english)? How could they be 404?
I don’t know how to manage all the other 404, example:
if I google http://experiencelabmilano.com/wp-content/uploads/social-media-partner-experience-lab-milano-7.png, I get a redirect to homepage: so, wht this url is in the 404 list?
I don’t know where to start from, hope you can help me.

Please check the screenshot:
https://pasteboard.co/IIiONLk.png
https://pasteboard.co/IIiP1wA.png

Thanks for your help
fabio