Can you please check if my sentences are OK? Thank you very much

1)I worked in a jym for one year ("a year" is a mistake?)
2)If you don't have a choice between two different parts do you say: What part did he play in the film Top Gun?
The film director (is "the" correct?) Kubrik offered him a part.
3) I spent my Christmas at my grandparents's house. In particular, I spent Christmas Eve with my grandparents and my family. My granny cooked a nice meal for us all.
4)As a starter we had breaded artichokes, then ham with melon and finally a salad consisting (made of) of boiled potatoes, peas and carrots mixed (?) in a mayonnaise sauce.
5)For our main course we had pasta with clams and mussels, then lentils with stuffed pig's trotter and finally eel with roast potatoes.
6)To conclude (better: as a dessert) we had a traditional Italian cake with raisins. We awaited the Midnigt playing cards, draughts (creckers) and bar billiards.

1 - "a year" would be fine, too.

2 - yes; and yes, "the" is correct.

3 - grandparents' (no extra 's' needed)

4 - "made of" is more casual; you can keep "mixed" or leave it out.

5 - commas after "course" and "trotter"

6 - "For dessert..."
We waited for midnight while playing cards, draughts, and bar billiards.