Hi there, 26y/o here.
Firstly, as advice for 21 guy, try a lot of things just like you are doing right now, to be honest it is unlikely you have a clear vision of you future career at this young age.
You haven't stated how much deep learning skill you have right now. Or you want to do research or try to be good at implementing stuff. I could be biased but I would suggest unrevealing your motivation and interest more before deciding next step. (Machine learning was really really hyped here in Japan, every student remotely related to CS like mechanical engineering studied deep learning and wanted to work on it. It was honestly over-hyped.)Not saying it is not important.
I can't say anything about Germany since I don't live there.
As for Japan, there are several start-ups hiring machine-learning talent, I have seen Germans here as well. But you still need a college degree in most cases.
Good luck, if you like new technology try block-chain as well.