英语改句子,用“he”作句子的主语,改的部分写出来就行了,

英语改句子,用“he”作句子的主语,改的部分写出来就行了,
麻烦把不是直接替换（可能要更换顺序或者加点东西的）的句子,说明一下为什么,
1、i have a new book
2、i shall see you tomorrow
3、i can understand you
4、i must write a letter
5、i may come next week
6、i do a lot of work every day
7、i did a lot of work yesterday
8、i played football yesterday
9、i bought a new coat last week
10、i have had a letter from Tom
11、i was busy this morning
12、i could play football very well when i was younger
13、i always try to get up early
14、i might see you next week
15、i always enjoy a good film
16、i had finished my work before you came
17、i watch television every night
我知道不能直接换，肯定要改变些什么，但就是弄不明白应该注意点什么？能告诉我变换的时候要注意什么吗？