Backup/restore partials (issues, commits)

after upgrading to 8.17 my gitlab instance get a complete mess: some part of gitlab can’t be accessed (error 500 appear). as long as version 9 appears, i do not want to “fix” it. i just want a new fresh installation.

i just need to restore 2 things: issues and commits. how can achieve this?

any help will be much appretiated.