What Vuedoc said.
Seventeen's not too far away from eighteen, it won't be long. As indicated above, eighteen's pretty much the magic age on this side of the pond. It may be different in Germany. If legality isn't an issue, consider maturity. She could emotionally older that her years and you may be younger than yours. That would make you more compatible. Consider her parents. I would not be particularly happy or acceptant of a seventeen year old daughter of mine romanticly involved with a twenty-five year old, to say the least. Some fathers could take extreme exception to it, possibly in the form of foot-to-a$$! And consider this- it would better for all involved if your approach is less Klingon and more Betazed. Use both heart and mind and try not to be so hormonal ...in other words, think with the big head not the little one. With thought and care the relationship could ultimately prove to be wonderfully Deltan!
'A screaming comes across the sky. It has happened before, but there is nothing to compare it to now.'