A free desktop service for organizing team work on projects?

Question

Helpdesk

Advise? We have an IT department of the beloved Post of the Russian Federation, we serve one post office.

Important:
1) Applications must be added by yourself, because. the qualifications of the operators do not allow to implement a full-fledged help desk.
2) There are 6 people in the department serving 87 departments and about 10 other objects.
3) The average number of applications per day: 15 - 40, before that they used the teamer web service, at first it was convenient, but after that a lot of garbage accumulated and we began to fall behind, besides, its functionality is very small.
4) Windows only.

Answer 1

Not satisfied with redmine ? Both free and functional above the roof and any operators can easily learn in it (tested on the example of one Bank where I used to work).

Answer 2

(removed)

Answer 3

Applications must be added

This is what I didn't understand. Do you want to add applications yourself? Those. system users will be only 6?
If so, you can buy Jira for $10.