You could use either and it would be correct. The difference is subtle. I would say that ‘in a meeting’ sounds more like a private meeting that you cannot leave. You might use this if you are at a work meeting. ‘At a meeting’ sounds more like an open more public meeting, perhaps a community meeting or PTA. I think you could use either and no one would notice.

I drink bottle of vodka. Fight with wall then sleep. This is Russian tradition.

There are no Christmas celebrations due to COVID19.

I work from home so my routine isn't that eventful honestly, but it doesn't mean my life is boring! My average day starts around 7 am. I have breakfast or study a foreign language. (I'm interested in four languages at once, so the practice does take time). what I do after breakfast normally depends on that day’s schedule, which is rather flexible. Working at home doesn't have to lead to lazy days; you actually need a great amount of self-discipline. After 8:30 I start working. During my working hours, I stay focused on my job. all of the household chores done in the evening. I dedicate different days of the week for different chores, which gives me a pleasant change in my routine. Today is Thursday so it will be laundry. After the chores I spend time on something pleasant and not related to my day's working routine.I like computer games, in my opinion, it's the best way to finish the day.