Looking at your gallery I dont think you need any courses.
If you want to know about exposures etc either ask the question in a forum or ask me,always willing to help.
There are probably hundreds of bits of info regarding exposures etc free on line.
As for marketing etc,that is a different ball game. Competition is fierce out there.
There are plenty of sites where you can put your images for sale,the downside is that you only get a pittance for your images. Maybe you should consider your own web site and shopping cart.
Seling one decent priced image now and again will give you more profit than selling dozens on image sites.
Eddie