Nonetheless I don´t really know how I can presell this to students, since there are just 2 exam periods each year. Are there any suggestions you would have for me?
Selling things to "students" is a lot harder than selling things to adults.
Students don't have money, are hard to deal with, and will all tell you they'll buy your product and then not come through.
If you're in college, I recommend exploring industries outside of your age group. Get a better understanding of what opportunities exist in the world.
Unless your idea is solving a significant need, and you know the money's there, I'd recommend broadening your horizons.