I would like to learn how to use better English expressions(11)

We had been talking for about an hour in my room when the feeling of delight escaped was not there and the room was just became enveloped in awkward silence. It was a curious thing, indeed. The atmosphere was had not been that bad. even when We met each other two years after we both (this simplifies the sentence.  It also prevents it from being a "run-on" sentence.) our entering the entered into military service. at the same period of time, Given that, we lost track of the time chatting over a drink. Probably Maybe (just sounds more natural to me)because we all felt awkward, we was were forced to smile.

I would like to learn how to use better English expressions, so I hope you can help correct errors in my writing.

To be honest when I read the first sentence I was very surprised in the word usage.  I'd even call it poetic.  I changed those words to add to the poetic nature of that sentence.  I hope my corrections still keep the meaning of what you were tring to say.  The one thing you could be more clear about is how many people you are talking about.  At first I thought it was about two people but at the end it seemed like more than two.  "because we ALL felt awkward" makes me think more than two.  

Are you saying that you met a friend after both of you finished military service?  Also you entered the military at the same time?  that was a little unclear at first.  Also, in the first sentence, was the feeling awkward the whole time?  Or did it become awkward after one hour?  I assume the second option.  If it was the first you would want to say "bout an hour in my room WHILE the feeling of delight..."  If that is the case, then replacing "when" with "while" would have been the only correction needed.  I hope my corrections were useful!  Good job though.

I would like to learn how to use better English expressions(11)

You have excellent corrections.  So for me to correct your entry, it will be of no added value.  So I am going to rewrite your intent in my own words.  Hopefully, this reflects your intent and show you another writing style.  Your last sentence is too long!  It is unclear.  Are you reminiscing another awkward time you two had? Or is it you are comparing the atmosphere of entering national service? Or is it that you are comparing this time with another time that you two met after two years of not seeing each other? Long sentences doesn't always mean good. Thus you can see different interpretations.

For an entire hour, we chatted in my room.  Then a cone of silence descended, displacing whatever delight that was there before.  A very curious thing indeed. We had entered national service around the same time.  We had drinks together. We chatted our heads off and lost track of time. Now, after two years of absence, this awkwardness is swirling around us, we had no choice but a smile forced to fulfill this obligatory social dance.

We had been talking for about an hour in my room when the feeling of delight was not there and the room was just enveloped in awkward silence. It was a curious thing, indeed. The atmosphere was not that bad even when we met each other two years after our entering the military service at the same period of time, given that we lost track of the time chatting over a drink. Probably because we all felt awkward, we was forced to smile.

I would like to learn how to use better English expressions, so I hope you can help correct errors in my writing.

-revised version-

We had been talking for about an hour in my room when the feeling of delight was not there anymore and the room was just enveloped in an awkward silence. It was a curious thing, indeed. The atmosphere was not that bad even when we had met each other for two years after we entered the military service at the same period of time.
We lost track of the time chatting over a drink and we were only forced to smile because we felt awkward.

~ I like how you use the term "delight". "the room was just enveloped in akward silence"- It can be mean as a metaphorical phrase. I only spot minor errors so great job! :)

I would like to learn how to use better English expressions(11)

We had been talking for about an hour in my room. when The feeling of delight (you can also use "happiness or joy") was not there and the room was just enveloped shrouded in an awkward silence. It was a curious (you can also use "strange or weird")thing, indeed. The atmosphere was not that bad even though when we haven't met (you can also use "seen") each other for two years after our entering the military service at the same period of time,. given that We lost track of the time, so we chatted (you can also use "talked") chatting over a drink. Probably because We both all felt awkward,. Therefore, we was were forced to smile.

I would like to learn how to use better English expressions., so I hope you can help me correct errors in my writing.