Hello.

It is a vulgar audio amplifier circuit, the arrow 3.3K resistor works as attenuator or does something else ?

 

Looks like It's part (isolation resistor) of an audio filter. Equal signals on the Differential IN+ and IN- results in no net audio output. For single-ended inputs, if we tailor the frequency transfer response between the two inputs we can change the frequency response of the amplifier at the output.

From the datasheet for a single-ended input signal.