It depends on one's capabilities. What you are learning, what learning materials you are using is a considering matter. No one can tell you that you need this specific time to learn forex. And moreover learning is a continuous process. Study everything available in School of Pipsology in babypips. It will help you a lot.
First you have to give time for learning. It's a professional work that requires specific knowledge and skills. Once you have necessary skilled, you can do it just by spending one or two hours per day. But for learning you have to put your efforts and dedication. One more thing learning doesn't happen in one or two months. You have to spend good amount of time depending on your level of understanding and other factors
Learning in trading the Forex market, I think, is a never-ending process. Even if you're able to consistently win your trades, there should still be room for improvement. If you're a beginner trying to become more experienced in trading, I think this will heavily depend on how serious you are in learning and how much time you actually want to commit to it. Because if you only want to learn it as a side thing, then the profits that you should be expecting should also be that, equivalent to a side thing. It depends on you, I say!