Giải giúp em vs ạ và giải thích cách chia các thì giúp e vs ạ

Exercise 3. Put the verbs in brackets into the perfect gerund or perfect participle. Examples: He was accused of (desert) his ship two months ago. - He was accused of having deserted his ship two months ago. (fail) twice, he didn't want to try again. Having failed twice, he didn't want ...