When you start to learn something new, a little and often is the motto. We learn better in small doses rather than bouts of intensive concentration. Especially body learning. There are no exercises in the Alexander Technique, instead you practise puttng your awareness into everyday activities.
It is difficult to say how many lessons you will need. Some people feel they have learned enough after 5 lessons, others continue for years. I suggest a course of 10 lessons.
There is no limit to the amount you can learn about yourself.