In the sentence of the text: “They will then be motivated to continue and keep learning” (lines 9-10), the pronoun they refers to 
The main idea defended by the author in the text is that 
The expression of the text “another tip” (line 5) suggests that the author 
In the fragments of the text: “they may lose the desire to master whatever task you are asking them to do” (lines 12-13) and “then you have to do more than just present lessons in the app” (lines 18-19), the verb forms in bold express the ideas, respectively, of 
In the sentence of the text: “However, if you want people to continue using the app, and use it frequently and often, then you have to do more than just present lessons in the app” (lines 17-19), the connector However can be replaced, without any change in meaning, by 
The boldfaced verb form conveys the idea of strong necessity in
