It’s great that you have had to correct the tense. It really shows how the language works.

Question 1. I see now how much more elegant your version is, “I was sitting at my desk playing”. Yet if you left my awquard version, would you say ”I was sitting at my desk. I was playing a game” or “I was sitting at my desk. I played a game”? I suppose it would be the former “I was sitting at my desk. I was playing a game”.

About your question…I wouldn’t break that up into two sentences. It flows, and is more to the point and tense of the narration by saying “I was sitting at my desk playing.” The sentence “I played a game” denotes finality to the action, and destroys the tone of narrating an action that was not yet complete.

Question 2. If your final version is “I was sitting at my desk. I was playing a game” how would you describe “I sat at my desk. I played a game.” Can the misuse of the tense be called a rude mistake or is it the way people often say that? Can this with the Past Simple be said by your neighbor, a bank clerk, your president or a teenager chatting in a bus? I would like to feel the degree of mistake.

I wouldn’t describe the misuse as rude, but simply unsophisticated. I would describe both ways that you wrote that as not being fluent or comfortable with English. You could say it to anyone under any circumstance and not be considered rude, and be understood, but you would be identified as a foreigner and someone not fluent in English. It’s a matter of fluency only.

Question 3. Are you sure that “I fought with Peter today” is absolutely correct? Could the boy have said “I have fought with Peter today”?

Yes, I’m certain that is correct. But it could also be stated as “I had a fight with Peter today”. You could also say “I have fought with Peter today”, but again it’s a matter of fluency. Saying things correctly in a short form denotes fluency and flows. Are you familiar with contractions? One could say “I cannot go to the movie with you”, and it would be correct, but it’s strict and unnecessary. It’s more conversational and fluent to say “I can’t go to the movie with you”. The former is considered haughty, and strict, the latter as comfortable and fluid.

Now that you have corrected my opus, Kevin, I deeply feel how important the correction of what one says is. I must have read and heared this pattern “I was sitting playing” a hundred of times, yet I have hardly payed much attention to it. As you saw I can easily go with my awquard “I was sitting and playing”. After correction it somehow gets curved in the person’s mind, I guess.

Your spelling is incorrect on one word, Lena: “awkward”, not “awquard”. Also, I’d say “…distorted in the person’s mind…” and not “….curved in the person’s mind”.