Hello, nice to see someone run into the same problem I had, it means I can help. My entry into the world of servos and micro controllers was similar.
Servos, straight from the store, work in roughly a 180 degree sweep, and the signal from the micro controller controls the POSITION.
Many servos can be modified for "continuous rotation" but there is a sacrifice. Position becomes unknown, the signal instead controls SPEED and DIRECTION of rotation. To have all of the above is a very expensive device. The best way to see if your specific servo can be modified (this is usually permanent), you will have to consult Google.