My MacBook turned off and even if I charge it it won't turn on.

I believe you are referring to an SMC reset. “SMC“ stands for “System Management Controller" and it controls how power flows through the components of the machine. To reset this, follow the instructions in the following image:

Since you have a 2017 MacBook Air, the next thing I would do is check to see if this machine is covered under AppleCare. You can check this by entering the serial number (located on the bottom plate of the machine) here:

https://checkcoverage.apple.com

If you are not covered under AppleCare and an SMC reset does not resolve the issue, there are a few other things you can try.

If you haven’t tried using a separate charger, try connecting a separate, known-good charger and attempting to power on.

If this doesn’t work, you may need to troubleshoot the internal battery. Open the bottom plate and disconnect the battery, then with battery disconnected and machine on its side, attempt to connect a charger and power on (be careful not to touch any internal components when the machine is powered on). If the machine powers on with the battery disconnected the battery may be failing and may need to be replaced.

Hope this helps!