Modify UI website and fix navbar issue on small devices (#4961)

-Fixed scroll issue on navbar:


https://github.com/twentyhq/twenty/assets/102751374/19f609f0-637d-483f-a695-f4a276155f2c

-Modified various UI elements, including design and layout adjustments
Example: 
**Before:**

<img width="279" alt="Screenshot 2024-04-14 at 18 45 04"
src="https://github.com/twentyhq/twenty/assets/102751374/c0f58aa6-440b-475a-bc85-69fef564f693">

**After:** 
<img width="312" alt="Screenshot 2024-04-14 at 18 45 17"
src="https://github.com/twentyhq/twenty/assets/102751374/2da4c2e8-e482-4d36-b6dc-02a51dde1950">

---------

Co-authored-by: Ady Beraud <a.beraud96@gmail.com>

packages/twenty-website/src/app/_components/user-guide/UserGuideContent.tsx

@@ -16,6 +16,9 @@ const StyledContainer = styled('div')`
     borderBottom: `1px solid ${Theme.background.transparent.medium}`,
     fontFamily: `${Theme.font.family}`,
   })};
+  @media (max-width: 810px) {
+    margin-top: 64px;
+  }
 `;
 
 const StyledWrapper = styled.div`