Do I have to study further?

You need to now get a job that will give you experience to do the high paying job. You may think you know everything, and you probably got A's on all your exams, but there are a boat load of work situations that you have never dealt with, and that all the college and graduate studies in the world will never prepare you for.

And if you take over the management of a company armed with knowledge that you memorized from a book, but no experience in the actual day to day operations, the chances are that you will make serious, business destroying mistakes that will ruin your job prospects forever.

Better to go in at a junior level, see what the high paid people are doing to mess up, and then learn how to not do that...and then take their jobs the second they mess up.

Study for as long as you like but you won't get a high paid job as you have no experience.
You have to start at entry level and work your way up.