shapemode doesnt help you in this case.
its only for loaded shapes (svgs)

what is important is where the shape is at the moment you want to rotate it. Because rotation always happens around the upper left sketch corner (coordinates 0,0)
so if you want to rotate something around its center, what you have to do is. translate it to 0,0 (or draw it there in the first place) rotate it, and translate it back. 

thank you,

ok I think I have a problem
because I want to have the shape somewhere on the sketh and the user can change its position.

Is there any solution for rotating a shape around itself?

like i said.
you can place it where you want it.
but for the rotation it has to be at drawn at 0,0...
look at this example. it rotates around itself but stays at the mouse position.



void setup() {
  size(600,400);
  smooth();
  background(255);
}

void draw() {
  background(255);

pushMatrix();
 translate(mouseX,mouseY);
 rotate(radians(frameCount));

  beginShape();
  vertex( -44., -37 );
  vertex( 40, -27 );
  vertex( 28, 26 );
  vertex( -20, 48 );
  vertex( -64, -20 );
  endShape(CLOSE);
popMatrix();
}

thank you, your code works but my code doesnt work:

pushMatrix();
 translate(mouseX,mouseY);
 rotate(radians(frameCount));
 beginShape();
 vertex( 59 , 11);
 bezierVertex( 59 , 11 , 51 , 0 , 33 , 0);
 bezierVertex( 14 , 0 , 0 , 15 , 0 , 37);
 bezierVertex( 0 , 58 , 15 , 70 , 34 , 70);
 bezierVertex( 52 , 70 , 59 , 59 , 59 , 59);
 endShape(CLOSE);
popMatrix();

it rotates around the corner....

yes, because thats where you drew it. the center of the object is not at 0,0
remove the translate and rotate in both examples and look at the difference. and their position related to 0,0....

Thank you!