I'm employed in a full time job where I actually work only 4 hours a day
Do you like working there?
The working environment is really interesting.
It is good that you are working hard and if you can manage to get your work done in a few hours it is okay. It provides a service to others.
I need to manage these guys. If they don't do the job on time, they can be fired.
That sounds like a tough decision. I would suggest giving a warning before flat out firing them if you can. You don't want unhappy workers to manage.