三个英文句子`我不明白为什么这么写

三个英文句子`我不明白为什么这么写
My father and I wacth TV.
My father with me wacthes Tv.
都是和我,为什么一个是用wacth原形一个加了es?
She is going to have piano lesson.
是第三人称,为什么用have?
Mary often goes shopping with her mother.
为什么shop要加ing?

第一个应该是主语的区别
My father and I wacth TV.主语是 My father and I
My father with me wacthes Tv.主语是 My father
第二个
going to 表示将要,后面跟动词原形,固定的用法
第三
goes shopping ,go 后面加动词的ing形式表示将要,固定的用法