I have a drinking party with nostalgic membersome old friends today.

I belonged towas in a volleyball club when I was a university student.

Especially when the senior members joined itattended, I enjoyed more than usual.

After graduating, there were a few parties with the same guys.

This year the volleyball team I belonged toused to be apart of before won the title.

I have a drinking party with nostalgic membersome old friends today.

nostalgic -> old (in this context)

I used to belonged to a volleyball club when I was a university student.

The members liked holding a drinking partyies and I ( often ) also joined itn.

join it = To attach multiple objects together くっつける
join in = To take part in an activity 参加する

EDIT: I think you were using the verb "join", in which case "join it" is technicially correct, but it sounds a little unnatural.

Especially when the senior members joined it, I enjoyed it more than usual.

After graduating, there were a few parties with the same guys.

I haven’t seen them forin a couple of years.

This year, that same volleyball team I belonged to before won the title.

It boosted my motivation to holding the old school party ( even more ).