Resizing the window and its contents

Question

I started studying PyQt5 and ran into this problem: it is necessary that the image stretches along with the window, and the buttons take the place of the blue rectangles and also change with the size of the window and image.

Here is my code. I thought about using the resizeEvent function, but so far I don't quite understand how to implement it.

from PyQt5 import QtWidgets, QtGui, QtCore
from  PyQt5.QtWidgets import QApplication, QMainWindow  
from K01_C01 import sect01
import sys

class K01(QMainWindow): 
    def __init__(self):  
        super(K01, self).__init__() 
        self.w1=QtWidgets.QWidget()
        self.setCentralWidget(self.w1)

        self.setWindowTitle("ECPT")  
        self.setGeometry(200, 100, 720, 405)

        self.picture = QtWidgets.QLabel(self)
        self.picture.setGeometry(0, 0, 750, 400)
        self.picture.setPixmap(QtGui.QPixmap("к01осн.png"))
        self.picture.setScaledContents(True)  
        self.btn = QtWidgets.QPushButton(self)
        self.btn.setText("C01")
        self.btn.setFixedWidth(150)
        self.btn.setFixedHeight(60)
        self.btn.setFlat(True)
        self.btn.setStyleSheet("QPushButton {color: yellow; "
                                "font: 28pt Times New Roman }")        
        self.btn.clicked.connect(self.C01)

        self.btn1 = QtWidgets.QPushButton(self)
        self.btn1.setText("C02")
        self.btn1.setFixedWidth(150)
        self.btn1.setFixedHeight(60)
        self.btn1.setFlat(True)
        self.btn1.setStyleSheet("QPushButton {color: yellow; "
                                "font: 28pt Times New Roman }")  

        self.btn2 = QtWidgets.QPushButton(self)
        self.btn2.setText("C03")
        self.btn2.setFixedWidth(150)
        self.btn2.setFixedHeight(60)
        self.btn2.setFlat(True)
        self.btn2.setStyleSheet("QPushButton {color: yellow; "
                                "font: 28pt Times New Roman }")  



        self.gird=QtWidgets.QGridLayout(self.w1)
        self.gird.addWidget(self.picture, 0,0,6,0)

        self.btngird=QtWidgets.QGridLayout()
        self.btngird.addWidget(self.btn, 0, 0, 0, 0)
        self.gird.addLayout(self.btngird, 2, 0)
        self.btngird.setContentsMargins(-100,-100,-100,-100)

        self.btn1gird=QtWidgets.QGridLayout()
        self.btn1gird.addWidget(self.btn1, 0, 0, 0, 0)
        self.gird.addLayout(self.btn1gird, 3, 0)

        self.btn2gird=QtWidgets.QGridLayout()
        self.btn2gird.addWidget(self.btn2, 0, 0, 0, 0)
        self.gird.addLayout(self.btn2gird, 4, 0)

    def C01 (self):
        self.wK01=sect01()
        self.wK01.show()



def application():  
        app = QApplication(sys.argv)  
        window = K01()

        window.show()
        sys.exit(app.exec_())

if __name__ == "__main__":
        application()