I can´t use a iTunes card from Germany in my spanish account What I can to do?

Send it to friends/family in Germany.

There's nothing you can do to use that card. iTunes cards and gifts are valid only in the country in which they were issued. As Chris said, all you can do is give or send the card to someone in Germany. If you want a gift card in your Spanish account, you'll need to buy a Spanish iTunes card (if Apple offers them in your country).

Regards.

Like Chris said, send it to freinds/family in Germany. 🙂