What about replacing jira+confluence+bamboo+bitbucket with redmine+gitlab+jenkins?

Question

git

Good!
Somehow, over the past half-year, the company has grown, and now they have come to quite large costs for Atlassian products. In addition, we want to raise Agile, HelpDesk, CRM and etc. There was an idea of ​​switching to redmine+gitlab+jenkins.
The questions are as follows:
1) Plz share your experience with redmine+gitlab+jenkins - impressions, features, problems.
2) Import jira issues and confluence records - yes, I saw it. that there are solutions, but how workable are they, how long to suffer with them?
3) It makes sense - www.redminecrm.com - how normal are the solutions, maybe there is something better?
Thank you!