Better help button behavior

**Is your feature request related to a problem? Please describe.**

When I am on the exchange page and click the "help" button in the bottom right corner, it always shows the hints of the exchange page even if I have learned all the hints and clicked "done" or "skip" and actually want to go to the main help page.

**Describe the solution you'd like**

Remember whether the user has done learning or skipped the hints. If yes, when clicking the "help" button, show the main / related help page. But what if the user wants to learn the hints again?

**Describe alternatives you've considered**

When clicking "help", show a sub-menu so the user can choose to show hints or go to the main or related help page.

Or maybe we add a "help" entry in the hamburg menu which always links to the main help page.

**Additional context**

Start at the exchange page's bottom-right help button and trace how hint completion or skipping is remembered and how the main or related help page is opened. Compare the proposed submenu and hamburger-menu alternatives, then define done as completed or skipped hints leading to the main help page while retaining a way to view hints again.

Written by the indexing model from the issue text.