You might find some Germans on the forum by doing a general search - http://forum.honeyflow.com/search?q=germany
or by looking in this section - http://forum.honeyflow.com/c/connect-with-locals
Germany harvest - Germany - my first harvest!
Here are some faqs for thixotrophic and crystallised honey:
https://www.honeyflow.com/faqs/do-flow-frames-work-with-manuka-jellybush-honey/p/103
https://www.honeyflow.com/faqs/does-the-honey-crystallise-in-the-flow-frame/p/69
When the Germans you refer to say it is too thick, ask them if it’s because of the flowers. Do you have rape/canola, heather, dandelion, etc?
If it’s just because of the cold, well the Flow frames have been used in very cold places across Europe, Canada, USA, etc.
If you want to do what Lori mentioned, here is the modification instructions - https://www.honeyflow.com/faqs/modifying-a-langstroth-box-for-flow-frames/p/143#a1
The other thing to remember is the Flow Hive is just in a Langstroth 8 deep standard size - so you can have a standard super and a Flow Super on there to test them.
Or you can have a Langstroth 8, 10 or UK national size hive, and add a Flow Super on in Langstroth 8, 10, or UK national size as well.
Now maybe you have too many options 