If I may add a comment as someone who is currently learning German, I think 2 years sounds like a huge amount of time. Let me explain my own learning situation to explain my answer.

Although I had some previous experience with the language at school (2 years), I left knowing almost nothing because it was not a useful method of learning for me. I then studied using audio courses, from time to time over 2 years, but wasn't really serious so didn't make any progress. 

I recently set myself the goal of being at B2 level by October and have been studying much more seriously, and most importantly much more intelligently. Next week I'll have a routine of speaking the language 5 days out of 7, some of which will have lessons, so I'll know what to work on.

So I'm aiming for B2 level in 5 months. And why not? I believe I can achieve it and I've set out to make it possible, so I think you could easily get to that level in 2 years, though I'd suggest a dealine that is nearer and make your goals both specific and achievable.