How to display another button after clicking on a button?

Question

PyQt

I decided to create my own game, and after pressing the button, everything closes and others are displayed, I made it close and put the button (all this in the def function), but in the end the buttons disappear and the others do not appear, what should I do?

def app(self):
    self.btn1.close()
    self.btn2.close()
    self.btn3.close()
    self.lbl1.close()
    self.btn1 = QPushButton(self)
    self.btn1.setMouseTracking(True);
    self.btn1.setText("Текст")
    self.btn1.resize(350, 200)
    self.btn1.move(-40, 1550)