应该是：
I teach them English by myself
亲自 by oneself
teach sb sth 教某人某事那么“我自学英语”怎么说？还有其中的by能去掉吗自学英语就是teach Enlish by myslef不是teach oneself sth吗这两种都可以, teach himslef English learn English by himslef 不过刚才把learn打成了teach