About Roundabout: who has priority?: which statements are correct? (multiple answers possible)
On a roundabout cyclists must always wait for cars, even when the cyclist is already on the roundabout.
Sign B6 and shark's-teeth already settle this unambiguously: the cyclist on the roundabout goes first.
/p.84 - only WITH sign B6 and shark's-teeth markings does traffic on the roundabout have priority. With no sign at all, the rechts-regel applies: entering traffic then has priority.
Whoever saw the roundabout coming first has priority over traffic already on the roundabout.
Explanation
Who 'sees it first' is not a rule — sign B6 settles this: the truck on the roundabout goes first (Book p.82).