Thanks for all the great replies and asking and answering the questions that I would have asked later when I got to that point. saved me a lot of trouble! Weird that googling for the answers didn't really give any good answers.
I love this community
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BTW, I am not sure why, but i don't have any problems with tiny cam asking for the login information after i inserted it once on the main admin account. never touched any settings about that.
I also found out that the dahua app has different options that you cannot acces when you have screen orientation locked. the zoom option is only able to be turned on in landscape and can only be used in portrait (don't ask me why, might have to do with my sony z3 compact phone or the app, can't test it now). I can't acces any options in portrait, might be a bug in the app.