After working for two hours, they were covered in dirt.
Or:
After working for two hours, the (men and/or women) were covered in dirt.
No 'Neither Bill or Susan say that the stove was working'
Yes, it is. It is a complete sentence. The preposition phrase (in the garden) is a valid adverbial phrase.
Work at the computer isn't correct language. But, work on the computer isn't a complete sentence. She/he is working on the computer, is correct. But of those two, option 2 would be fine.
"Our microphone is not working," said the announcer. (removed stupid/ignorant comment)
Subject = she verb = is working
While you were working she arrived. When I was working on x project she arrived. She arrives on time daily.
Example sentence - The men in the workshop were working on different parts for an old fashioned covered wagon.
No 'Neither Bill or Susan say that the stove was working'
If you were saying this, would you pause before you said 'as well'? If so, put a comma. If not, don't. If this is the whole sentence, a comma is probably unnecessary, as there is not really any possibility of misunderstanding. But if it is part of a longer sentence, read through the whole thing and consider where the pauses would naturally fall.
The second sentence is the correct choice: "John has been working here since August." This sentence conveys a continuous action that started in the past and continues into the present. The first sentence does not correctly express this ongoing duration.
No, "diligently".
Yes, that sentence is correct. It expresses eagerness for a positive professional relationship with the person it is directed towards.
Yes, it is. It is a complete sentence. The preposition phrase (in the garden) is a valid adverbial phrase.
After working in the garden all day, her hands were covered in grimy dirt.
the correct answer is: I am interested in working....
No. She is working. She has been working.
I slept on the chair for a good thirty minutes while working on the computer because I foolishly fell asleep.