AnalogWrite not working in if statement
ORIGINAL RESPONSE, BASED ON DIFFERENT CODE

You are comparing sensorValue to see if it's ever less than minValue.

However, you have mapped sensorValue to range from 0 to 255, and minValue is set at 0. How can anything from 0-255 be less than zero?

NEW RESPONSE, BASED ON UPDATED CODE

One of your if statements: else if(sensor = baslangic) is not comparing, but assigning baslangic to sensor. To compare, use ==.

Your other if statement: else if ((start &lt; sensor &lt; maxval)) is wrong. C++ doesn't work this way. Maybe you want: if ((start&lt;sensor) &amp;&amp; (sensor&lt;maxval))? 

Instead, your statement evaluates like if ( (start&lt;sensor) &lt; (maxval) ), which means you are comparing the TRUE or FALSE of (start&lt;sensor) to the int that is maxval.