No offense, but for someone in college working on a thesis you should've noticed this in your linked post:
Before you can use the sensor, it has to be calibrated. For this, connect the sensor to your circuit and leave it powered on for 12-24 h to burn it in. Then put it into outside air, preferably at 20°C/35% rel. hum. (humidity is not so crucial). Read out the calibration value as such
float rzero = gasSensor.getRZero();
Do some research before asking help on your thesis. I don't mean to be a jerk, but as a college student myself, it's rather insulting for you to ask a question that is answered in the link you posted.