So lost

[Axel_Erfurt]

do

pip3 show pyqt5

my output is

Output:
Name: PyQt5
Version: 5.11.2
Summary: Python bindings for the Qt cross platform UI and application toolkit
Home-page: https://www.riverbankcomputing.com/software/pyqt/
Author: Riverbank Computing Limited
Author-email: [email protected]
License: GPL v3
Location: /home/brian/.local/lib/python3.6/site-packages
Requires: PyQt5-sip
Required-by: 

if your output is not empty try an example

from PyQt5.QtWidgets import (QApplication, QMainWindow, QMessageBox)

class MainWindow(QMainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.setWindowTitle("Test")
        self.setGeometry(50, 50, 250, 150)


    def msgbox(self, message):
        QMessageBox.information(self, "Message", message)


if __name__ == '__main__':
    import sys

    app = QApplication(sys.argv)
    mainWin = MainWindow()
    mainWin.show()
    mainWin.msgbox("it works")
    sys.exit(app.exec_())