忘记做某事用英语怎么说

forget to do something 忘了做某事
forget doing something 忘了已经做某事

forget to do sth.

I forget to have my lunch .我忘了吃午饭了.
I forget having ny lunch .哦,我忘了我吃过午饭了.

forget doing something 忘了已经做了某事
forget to do something 忘了去做某事

forget to do sth. （绝对正确）

forgot about....