1 . I learned that they can be extremely useful and educational.
2 . By reading vocabulary and expressions about app creation.
3 . I learned the word 'relatable', using context clue it seems to mean something that relates to something else. I also learned 'intertwined' which I understand is something based on another thing or that has something to do with it.
Also, 'worthwhile', it seems to refer to something with value.