Problems with analog port reading flame sensor and mq2

Hello to all,
Are the first weapons with Arduino. I tried to put the flame detector and the Mq2 sensor (gas detector) but having followed several tutorials does not change my reading value. In the serial monitor I always get the same values. The links look just, I've tried different. I also changed board and sensor. What is wrong?
Thank you

Do you mean this ?
Grove - Gas Sensor(MQ2)

It looks like you are using Google translate or similar and it is not very clear what you say.

This is a gas detector and there is a tutorial at the link above. Have you tried this tutorial ?