Python PyQt update GUI

Question

basically I am having trouble with Updating my new GUI. Windows 10 | Python 3.8 | PyQt5

I got a class like

class My_GUI():
     def __init__(self):
          ...
     def callback_func1(self):
          self.tabWidget.setCurrentWidget(self.tabWidget.findChild(QWidget, "tab_2"))
          func2() # does some file operations in the background
          self.tabWidget.setCurrentWidget(self.tabWidget.findChild(QWidget, "tab_1"))

That callback_func1 is connected to a QPushbutton.clicked - Signal, so i push the button and it is running.

And here is my problem: I would like to first switch the tab in the GUI to tab2, then call func2 (which is not a class method and not using the object ) and then switch to tab1.

But what happens visually is: I just see the switching to tab1 in the end (after func2 needed its 2 minutes to run). So the first tab change never happens.

I think the problem is that the windows shows changes just after the object was returned from the callback function

--> How would you solve this? Is there only the option to do something like Multithreading?