Disk usage

Hello everybody,

I have issues with our company website http://www.siz.it
We are a printing company with a wide portfolio of books/editions.
We have over 930 mb in wp-content folder and a maximum hosting of 1000 mb. Every time I have storage issues as I finish free disk space.
I want to understand:
– Is 1000 mb too few?
– I see that for every image there are several resized images: I understand this is meant to make the website faster, not needing to resize the images when somebody visits the website, is this needed? do I’d need to disable this option? How can I disable it?

Please let me know!!

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