[DE] Update Main page

[The-Last-Cookie]

Improved some phrasing here and there.

Tried my best with handling bespoke music

Self-check

• The changes are tested against the contribution checklist
• (translations only) The changes are reviewed on GitHub by a fluent speaker

[osu-wiki-observatory]

Your translation may be missing new information from corresponding English articles. Please update your translation according to the merged changes:

• Move and clean up Silence #12441, files:
  • wiki/Main_page/en.md

[osu-wiki-observatory]

Your translation may be missing new information from corresponding English articles. Please update your translation according to the merged changes:

• Add Tournament Committee user group and pluralise the User_groups page #12800, files:
  • wiki/Main_page/en.md