[BUGFIX][ENHANCEMENT] Various bugfixes

[notsure]

Pull request

• Changed translation keys
• Changed all possible css definitions from px to rem

Ticket

• Fully switch to use REM in css #161

Browser testing

• link

Checklist

• I merged the current main branch (before testing)
• Added JSDoc and styleguide demo
• Tested all links in project relevant browsers
• Tested all links in different screen sizes
• Did run automated tests and linters
• Did assign ticket
• Double checked target branch

Review/Test checklist

• Did review code and documentation
• Tested all links in project relevant browsers
• Tested all links in different screen sizes
• Did check accessibility (Wave, only errors)
• Re-assign ticket to developer

[thomasender]

LGTM