my part time job

I work in a supermarket as a cashier four times a week. But these days I am busy because of the club, a lot of homework, and so on. So, I can't work much and do my part time job only twice a week. I guess that I won't get a good pay this month. One of the reasens that I can't do my part time job is that we sokyoku club will have a regular concert on December and we are busy now to prepare for that. We practice three times a week these days and I can't have my job on weekend. After the concert have finished we don't have club activities until February so I can do my job on the end of the year and the beginning of the year, I want to get good salary to pay the costs of preparering the concert.
I have been worrying about the difficulty of the relationship with other workers of the supermarket, because there are many women and men who are older than I and  I'm not used to have conversation with them. There is a difference between "partner workers" and "part time workers" that the former is the official staff and most of them are mothers generation and the latter is not the official member and most of them are students like me. We rarely have the chance to get to know ourselves better because work times are different from each other in even ten minutes and we dodn't meet in a tearoom or locker room. So we don't enough time to contact with each other.
These days I gradually become used to my job and I can enjoy talking with the workers. I think that it is a good thing to talk with elders and get a various ideas because I always talk with youngs and eat with youngs and study with youngs, I rarely have the chance to pass the day with elders. Actually it is interesting to talk with women and men older that I and I am glad to learn a lot of things from them.
Yesterday I had a part time job from seven o'clock p.m. to ten thirty p.m. and I went to a drinking party with other workers (of course, I didn't drink!) I didn't expect to go but a worker invited me to the party and joined in it.  At first I felt nervous because, of all members of it, only I was a part time worker and there are some mem who are not the same work (there are some part of work, e.g. cashier part, fresh fish part, glossary part, flower part.) But they are kind and I enjoyed this party. After the drinking party finished we went to karaoke and stayed there until three o'clock, I was execited and didn't feel sleepy but they are older then I and maybe they wanted to go back home. I feel sorry to them worrying about that I may make them go to karaoke with me. If this is true Iwant to apologize to them. They are kind and they said that they enjoyed too, but I am doubting them. But I enjoyed and actually I am feeling happy to get to know better each other, I hope to make a better  relationship with them. Thank you! (Oh, I didn't pay at all! Also thank you!)