If your native language is English, give German a try first. German’s my second language and I started learning it at 19 (even though I’ll be 60 in about 3 weeks) just because I liked it. There’s more opportunity to speak Spanish in the US, but I personally like German better. It’s similarities and differences compared to English are kind of fun to learn, and I just love the people and culture of Germany. And that makes a big difference too. It’s fine to want to learn two languages at the same time, but it’s not like trying to decide between two different pairs of pants to buy, so you buy both and alternate them. You don’t want to bite off more than you can chew, because what will happen is you’ll get frustrated and give up learning both of them.