Like the others already mentioned, it depends on the languages you already speak. I see that you have a pretty high level of English, which could make German easier, but also a high level of French, which can help you with your Spanish.
It also really depends on your motivation though. German could be a lot easier for me, since I'm Dutch, but I lack the motivation to study it. Spanish is more difficult, but I enjoy that language so much, that I can spend hours studying it, reading books, watching shows, talking to natives.
Go with what you want to study most and you will succeed!