Well that's hard to determine I studied English in an international institute with different students nationalities what I observed about each student improvements was completely different than what I believed There were students who keeps studying and do homework regularly And there were careless students. But that's not a factor of improvement. The Main factor according to my observation was whoever English was their hobby in other word enjoys studying English improves so quickly that they could finish a 6 month course within 3 months

it depends, a good teacher should be giving you tools to improve on your own without relying on lessons. With that in mind, you should see progress quite quickly. The teacher´s job is to monitor that progress.

Hello! I think it depends from students abilities and their passions to languages. But let's be honest, B1 is not a high level and you'll definitely need to spend 1 or 2 years of EVERYDAY learning. It's almost imposible to gain sufficient amount of vocabulary within less time. Look at level descriptions at Common European Framework of Reference, CEFR and compare B1 and C2. I think you will understand that there is a huge difference between them.

There is no set rules on how many sessions a student needs to progress from one level to the next. It depends on the student's aptitude, Some are quick learners which is an inborn trait. Patience and determination to learn also help. The teacher guides the student along the way.