Because nowadays you have to ask for permission before you get the list...
Taifun
I have all the permits.
the old application does not ask for permissions and still works
I downloaded the app and code from this video. The old apk works, but the new apk does not work after building and donwload.
I set permissions on my phone.
It was built with an old target sdk
If you build now, you have to ask for permissions
Taifun
Well, what about following the link to see how to do it?
Here is it again...
Taifun
Sory I don't understand what I should do. it works, but I have no idea how to implement it into my program. I'm on my first day at this
Well, are you able to click a link?
This one from my previous answer
You can find there the recommended blocks how to do it...
Taifun
Yes, and I ran it and it works fine. I have a list of devices all over my screen. I can't do anything else on the screen. I can't see the buttons underneath
Great
Yes, the listpicker will use the complete screen to display a list of devices
Now usually you pick one of the devices you like to connect to
Taifum
I learned a little more about this app. Unfortunately, when I go into that article, I donwload the app BTclient_test2. It shows me a list of devices. Unfortunately, it still does not connect to the HC-05 module for Arduino. I have allowed all options in settings
Did you meanwhile ask for permissions as mentioned several times earlier?
It would really help if you provided a screenshot of your relevant blocks, so we can see what you are trying to do, and where the problem may be.
To get an image of your blocks, right click in the Blocks Editor and select "Download Blocks as Image". You might want to use an image editor to crop etc. if required. Then post it here in the community.
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.
Yes, it asks for access, I allow it. I see the HC-05 device in the app, when I click to connect, nothing happens
Switching Screens breaks Bluetooth connections.
How to prevent this?
Use virtual screens or establish the Bluetooth connection on the relevant screens.
I created Virtual windows. Unfortunately, when the link opens, it still shows me a list of devices, I can select it, but nothing connects. When I try to press the button, an error pops up
Where is the ListPicker1.AfterSelection Event block where you should be doing your Bluetooth connect?
The entire connection is copied from the project they referred me to. I don't fully understand why it works this way. Could you direct me more precisely where to look? In the guide on YT, the entire connection takes up one small block and it works for them, but I understand that it is intermittent.