Cart is not updated when we navigate from page to page.

Hi,

This indicates that the pages are cached and since the cart module is displayed together with the rest of the page, when the whole page is cached, when someone displays a previously cached page, he sees the cart module from when the page was cached.
And the cart module displays the correct thing after an add to cart because in that case, the system will refresh the cart module area with the current content dynamically.
You need to turn off full page caching on your website if you don't want that to happen.