If you dont mind, I could ask some people to translate the full letter
From what I can tell myself, the writer was very close to Frieda Hoffmann (his girlfriend ? sister?) as he addresses her as “Dear Frieda”
The letter ends as follows :" (I) wish you a verry happy christmas in advance, see you soon"
As for the value of the card, there is not really anything important written on the card (like military information, news from the front) , the soldier seems to just thank the woman for something, wishing her a happy christmas if there is no time inbetween to receive/write letters. It is an interesting card design, being drawn by a soldier of the unit, but overall (at least here in Germany) nothing to special. Here in Germany such letters go for about 8-20€, a bit more if the card is interesting/ the unit is rare. Unfortunately I cant tell you more, as it is not really something I collect, although me personally, i would give someone around 6-8€ this card