I suspect this is a really dumb question, but first the background details
Device: Vollaphone Quintus
O/S: VollaOS 15
Other related apps: Messaging
Affected app: Congstar 6.12.0
Attempts to solve the problem: Not many... I don't know where to start. I did try a number of Internet searches and tried looking for an option to put Congstar into the "background" but found nothing relevant.
Details:
Congstar is a mobile phone provider and subsidiary of Deutsche Telekom. I installed the Congstar app to find out exactly how much data I download and upload in a month. To access my account information I need to login. When I enter my username and password, Congstar sends an SMS with a code for the 2FA. At this point I have to switch to the Messaging app to get the code. When I go back to Congstar, the app wants me to start the login procedure again and the code is, therefore, useless.
What I would like to know is how to access the Messaging app without implicitly closing Congstar, which is apparently what is happening. I suspect it's a dumb question because I see or read about people doing this sort of thing in various movies, shows, novels, and so on. Therefore, I think it's something that is very common, just I have no experience in doing it.
Any tips would be very welcome.