Had enough!!!!

I am a U. S. citizen living in Mexico for the last 8 years, with my 10 year old daughter. Her father and I split up when she was 2 years old. My daughter has always lived with and been supported only by me. Her father is from Germany. Two years ago I allowed her to go to Germany to visit him.... not only did he not return her to Mexico as we agreed, he also cut all contact between us. When I went to Germany to find her.....he hid her away from me. Long drama story short.....I won full custody of her in a German court this past June and she is back with me. Her father has now filed an appeal with a higher court in Germany. I have had enough of this. I have no money or desire to return to Germany to fight his appeal. She is happy to be back home.
What are the repercussions if I ignore this appeal?
I was told, by a German lawyer, that my case can´t be heard in Mexico because it is already started in the German court system.
Any suggestions or help please?

The lawyer was correct. Unfortunately, if you do not show up in court, you will lose by default, and he will be awarded custody of the child. You may have had enough, but if you stop fighting at this juncture, you risk losing custody of your child again. You need a good attorney now.

She may be able to hire a german lawyer and "appear" via video or tele conference. Good luck.