I was advised by Tanja (in German), and I would recommend Travelnation.
Friendly and individual service and a lot of patience with every change of the itinerary and every question, while there was no urge to book (unlike other organisations). No problems with booking, and they offered the cheapest flight departing from Germany of all four travel agencies (others are STA Travel, Roundtheworldflights.com, local travel agency). The only negative aspect: They offered the most expensive insurance while the cheaper ones were only mentioned on demand.
But all in all I'd book there again.
Thank you Tanja (and Chris)
PS: Beratung bei Tanja auch auf Deutsch möglich!
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