For those who are interested
I purchased cells in China instead. It was cheaper than buying them in Germany. Although I have to pay duties and Danish VAT.
http://www.bmsbattery.com/Per battery inc. freight and duty
In Germany for a Headway LiFePO4 3.2V/16 Ah cell: € 31.83
In China, for the same cell: € 30.5
Besides, I needed a
BMS and I have only be able to find one large enough in China.
So now I have to wait for it to arrive, so I have to can get started building.