english question-when....

the latter one "when we have meal" is correct. When we having meal is incorrect since there is missing "are" in front of having to complete the tense

At the same time, even if we write when we are having meal, we will not usually say it this way. Just like breathing, because we breath every day, so we do not need to say when we are breathing, and we can simply say when we breathe. Therefore, it is more common to say when we have meal.