the i2c chip is PCF8574T.
when i used the potentiometer in back of the module, the screen become more dark, but nothing is write on it
i used a lot of library but no one works
You need to be very methodical. i.e. don't change/try so many things all at once.
My suggestion, install the library referenced on their page.
I looked at the code and the board layout and they match so that code looks like it should work.
(At least it appears to be putting the lcd data and control lines on the proper output pins on the i2c chip)
Make sure to remove any other i2c lcd libraries to ensure you know which lcd i2c library is really
Look carefully at the i2c part. Who makes that chip? and it is a PCF8574T or a PCF8574AT ?
Different chips use different i2c base addresses.
Perhaps it is the AT chip?
If so, the i2c address should be 0x3f instead of 0x27