How can I connect 5 flex sensor to Arduino? One sensor to each pin (A0, A1, A2...)? I have got problems with the codes in the sketch as well.
Yep one to each of 5 analog pins, with the sensor as one side of a potential divider. The junction between the sensor and the other resistor goes to the pin.
But we can't guess what your problems are until you tell us. Have you seen this tutorial?