The reference to Aachen was to the local Fairphoners group, especially @urs_lesse, who is organizing frequent meet ups.
Those meetups are a good opportunity to get a hands-on with the Fairphone 3, get background information and reports of experiences by users plus meeting interesting people and have a nice chat and evening.
The one thing you can not do during those meetings - as far as I know -, is, buying a phone.
But if you have had the chance to touch, feel and test the phone plus the chat with real Fairphoneers, you sure will be able to decide if this phone is for you or not.
And then you can safely order online.
Edit:
If interested, take a look for the latesd updates / meeting infos here:
(last meeting has been on 4th December).