How long does it take to move from one level in English to another?
A top Cambridge researcher says a motivated adult learner can usually do this with between 100 and 200 hours of "guided learning" (classes, homework, and other recommended tasks).
However, it generally takes less time to move from A1 to A2 than to move from B1 to B2, or from C1 to C2. (This is why intermediate and advanced learners sometimes feel like their progress is a bit slower).