I have set the “max-width” to 450px and removed the side navigation bars and changed the top navigation bar and all widths in the @media CSS are set below 450px.
What you did is not enough.
Your site still wider than screen on mobile devices.
Top menu, footer, product description - these elements remain too wide.
Add another rules for them.
As said above, you haven’t accounted for all of your elements in your @media rules. It’s best to do the @media rules along with the desktop layout, as it’s otherwise too easy to forget to change widths and other settings on a lot of elements.