Let’s say somebody asks me a question:
Yesterday was a party at your home. How did your girlfriend help you?
Which answer should I prefer? - :
She was washing the dishes yesterday.
She washed the dishes yesterday.
My take on your question:
Since the question reads “how did she help you?”, you ought to respond with “she washed the dishes”.
If the question read “why wasn’t she with everybody at the party”, a response would be “she was washing the dishes”.
Hello, Shaky:
(1) I think that the word “yesterday” shows that we are referring to an action that was done (and finished):
Yesterday, I cooked the food and she washed the dishes.
(2) I think that the progressive/continuous sentence would show something “in progress” or “continuing”:
Yesterday, she was washing the dishes when I came into the kitchen and gave her an engagement ring./ When I walked into the kitchen with my surprise, she was washing the dishes and had no idea about the ring.
James
OK.
But. Would it be wrong to say? -:
While we were eating the cake, playing cards and singing new pop hits she was washing the dishes.
Hello, Shaky:
IMHO, your sentence is fine:
While we were having a good time (eating, playing cards, singing), my girlfriend was washing dishes in the kitchen.
Of course, if you guys had a good time for 2 hours, I don’t think that your girlfriend spent two hours washing the dishes,
so maybe it might be more accurate to say something like:
While we were having a good time, my girlfriend washed the dishes and then she joined us in the fun.
That is, you guys started the fun at 6 p.m. Your girlfriend started washing the dishes at 6 p.m. She finished at 6:30. Then she
came in to join the fun, which continued until 8 p.m.
Of course, here in the States, males and females are equal. So probably some American ladies would prefer this sentence:
While my girlfriend and our friends were having fun in the living room, I washed the dishes (and then joined them). 
(I learned
that smile symbol from someone at this website.)
James
Well. Talking theoretically about two tenses simple past and past progressive am I right saying:
Simple past uses action as a solid unpartable thing to describe something in the past that had been finished.
Past progressive can be inside of the period of time in the past and never marks the end of action by itself.
This is just my thoughts.
Hello, Shaky:
(1) I like TRYING to answer your questions because it is I who learn so much. You probably know that saying: If you want to learn something, try to teach it.
(2) I think your definition of the past is spot-on. (I recently learned that the British people use “spot-on” to describe something as absolutely correct. I like it very much.) Regarding your definition of the past progressive, it seems quite good. (I also recently learned that when the British people say “quite good,” it means: it is good, but …)
(3) I got this from English Review Grammar by Professor Walter Kay Smart:
When one action of brief duration occurred while another action of longer duration was in PROGRESS, the briefer action is in the past, the longer in the progressive:
He WAS WAITING for the train when I SAW him.
(4) The professor then explains these two sentences:
He SPOKE as I ENTERED the room. = He made a brief remark (maybe a greeting) when I entered.
He WAS SPEAKING as I ENTERED. = He was in the midst (middle) of a statement that he had begun BEFORE my entrance.
(5) Shaky, it’s great that you want to really understand the difference between the past and the past progressive. Keep posting questions in a new thread until you understand the difference. I PROMISE not to answer your new threads about this matter. I want a language professional to give you a really good answer about the difference.
James
James cool answer. Many thanks.
I got much new from your post.
Really helpful.
Never thought it was correct to say -
He SPOKE as I ENTERED the room
Turning to my definition of past progressive I haven’t seen in your samples that progressive tense was interrupted by itself only by simple past.
I gonna to read something of Professor Walter Kay Smart
Hi James how are you ?
All the animals in the world , only human can live longer if he wishes , do you have that idea ?
It does not mean a man is immortal but I want to say he can live slightly longer than who does not want ! That was why 'Shakespeare 'once said - a coward dies many times before his dying .
'When R was watching TV, Martha was sleeping ’ we do not know 'how long did they act their such activities last night ?. When the detective entered the room both were lying on the couch -just senseless .
Do you think first one -like ‘when R—’ this complete sentence context was correct ?If so ,why can not we use two parts of progressive tense in the past ?
As I know here ‘When R…’ had better be ‘While R…’.
And I am sure it’s possible to use two parts of sentence in progressive past tense.
Let’s wait on pro’s answer.
Thanks, Tshirt, for your interesting note. Like Shaky, I am waiting for an answer from the pros, too.
James
Hi guys,
While you’re waiting for the pundits’ reply, here is the view of Prof. R. A. Close on the progressive aspect:“Whether, in ACTUAL FACT, THE ACTIVITY OR SERIES is completed or not, is irrelevant: what is important is that, in using the Progressive, the speaker is concerned with the uncompleted part of it, or the temporary duration of it.”
And on Past Progressive:“This is simply an application of progressive aspect…to past tense. Then: I lived/was living in the country in 1972. George was getting up at five o’clock every day that week. The Rhine was flowing unusually fast that day. I was telephoning George Lamb only an hour ago.” Thus, “…was washing” sounds good placed in an isolated sentence, or if you mean the set of washings during the evening. Compare:“Hurry up. The caretaker is closing all the doors” /series of acts./
P.S.While typing and rereading it, I began to understand something myself - exchanging with ideas is a profitable activity, James, you are right.
Regards.