Student or Learner
tomorrow i finishes my work at 8:00 pm so i won't be able to go with you
because i'll have been working - for - the all day
because i am going to have been working - for - the all day
so is the grammar here right ?
and is -for- optional in these examples ?
It's correct to say "my work", but, typically, more natural to not say it.
I used "I finish work at 8:00" because the simple present (first form) can be used to talk about things that are scheduled or fixed times. It's possible that the speaker is scheduled to finish work at 8:00.
Here are some other possibilities:
1) "I'm finishing work at 8:00 tomorrow, so I won't be able to go with you."
We can use a progressive form (present) for a future activity or event that's planned or arranged.
2) "I'm going to finish work at 8:00 tomorrow, so I won't be able to go with you."
Use "be going to" for a plan - something that is already decided.
3) "I'll be finishing work at 8:00 tomorrow, so I won't be able to go with you."
Use the future progressive in the same way we use the present progressive for a future action. Using the future progressive emphasizes the continuing or ongoing nature of an event or action. It's possible to view "finishing" this way depending on what is required of one to finish. Or maybe the speaker is not 100% sure of the time, so chooses to state as a very, and relatively, short-term action or event. This would be the least likely form to use in this situation, but it is possible, and people do use it in this way.
Tomorrow I'm not going to finish work until 8:00. And by that time I'll have been working for 14 hours, so I won't be able to go with you because I'll be too tired.
I used "I'll be too tired" because the speaker is stating a certain prediction in his or her view.
Saying "I won't be able to go with you" is a certain kind of promise (or maybe a certain prediction) which is another reason to use "will".