「ある」 can be used as a descriptor to mean “an existing” or “a certain” (ex: 「ある本」 means “a certain book” or “a book that exists”)
the て form can be used to connect clauses like “and” (ex: 「つまらない本を読んでいて。。。」 means “is reading a boring book and…”)
the tense of the final verb in the sentence determines the tense of all the verbs
「くれる」 means to give “downwards” (to me or my group)
「あげる」 means to give “upwards” (to someone else)
the て form can be used to describe an action done for someone’s benefit by using the て form and adding 「くれる」 or 「あげる」 depending on the direction of the action (ex: 「遊んでくれなかった」 means “did not give the act of play”)