Help with handling text data between screens

Please i want to create an app that will have only two Screen

the first screen will contain list of buttons

the second screen will contain a LABEL

i will upload a .txt file

when first button is click it will open the second screen with and set the label text to the first line on text on the .txt, until it encounters a double space then it will stop reading.

when second button on screen one is click it will read the second line until it encounters double spacing. like that.

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There is a free programming course here Course In A Box and the aia files for the projects in the book are here: App Inventor 2 Book: Create Your Own Android Apps
How to do a lot of basic things with App Inventor are described here: How do you...? .

Also do the tutorials Tutorials for MIT App Inventor to learn the basics of App Inventor, then try something and follow the Top 5 Tips: How to learn App Inventor