I need help with calibrating this sensor. Is there anyone who can help me;

Well yes, I can lend to. Have you tried entering, into your most favored internet search engine, the words “SENSOR MH-Z19B calibration”?

You ill get links such as to the datasheet, where the topic 8.ZERO point calibration, might be of some help, or you can find other useful information such as:

void setAutoCalibration(bool autocalib)
MH-Z19 has automatic calibration procedure. the MH-Z19 executing automatic calibration, its do zero point(stable gas environment (400ppm)) judgement. The automatic calibration cycle is every 24 hours after powered on.
If you use this sensor in door, you execute setAutoCalibration(false).

void calibrateZero()
execute zero point calibration. if you want to execute zero point calibration, the MH-Z19 sensor must work in stable gas environment (400ppm) for over 20 minutes and you execute this function.

void calibrateSpan(int ppm)
execute span point calibration. if you want to execute span point calibration, the MH-Z19 sensor must work in between 1000 to 2000ppm level co2 for over 20 minutes and you execute this function.

And that is from only looking at 2 links out of the 14,100,000 results.

have you used the winsen pdf and it was helpful??? because neither for me nor for lot of others seems to be working. There is coding in those million results you mention but full of mistakes.

So since I need some serious help, because I need to use it in a high school activity. I would really appreciate it.

Instead of looking to someone else to do your homework, go get one of those code thingies with mistakes, load it up, and post the code and the mistake here and Some One should be quite helpful in helping you figure out what is the point of failure.

I have not used the device in question, I did find the product spec useful. I figured out that to get a proper calibration, you have 2 options.

One you will need a isolation chamber that has 400ppm of C02 and let the sensor sit in that enclosed chamber, whiles powered, for 12 hours, blah, blah, blah.

Two, use the built in calibration routines, found in a library, that access the factory calibration values.

For "serious" help, please take this forum seriously.

Start by reading and following the instructions in the "How to use this forum" post.