Hello. I will really appreciate some help.

1)Which preposition is correct in the context "to work at/in a company"?
2)Is it "a vacancy at" or "in our company"?
2)Which is the correct word order in the following word-group: "British TV dance show" or "British dance TV show"?
3)What articles would you use in the context: "Her task was to write a (the?)scenario for/of a (the) farewell party"?
I would opt for "a", is it possible? And which preposition is natural, "for" or "of"?
Thank you for all your help and attention.

1) "to work for a company"

2) "a vacancy in our company"

2) correct word order = "British TV dance show"

3)What articles would you use in the context: "Her task was to write a (the?)scenario for/of a (the) farewell party"?
If you use "a" as the article, then you are referring to a hypothetical situation. If you use "the" as the article, then you are referring to a real situation that will happen in the near future.

I would opt for "a", is it possible? And which preposition is natural, "for" or "of"?
Use "for" not "of."