Replace mock texts with proper messages

[theovier]

Description

Reason for this PR

• The messages in the profile and account creation were mostly mockups.

Changes in this PR

• Replace mock texts with proper messages that should give the user a good overview over the sections.

Type of change

• Refactoring

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Manually tested all use cases this could alter

Test Configuration:

• OS: Windows Mac Linux

• Browser: Firefox Chrome Safari Chromium

• Frontend:

  • Development build

• Backend:

  • No backend needed to test this

Checklist:

• I have performed a self-review of my own code
• My changes generate no new linting warnings or console warnings
• I have updated the CHANGELOG.md to include any changes made in this PR (add WIP to the top, if there is none already)

[tobias-wiese]

You could additionally adapt the info texts in the course form as well.