Need ruby on rails expert

Iam getting the following errors in ruby on rails see versions below: ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux-gnu] Rails 5.2.1 Error: Unknown database adapter `mysql2` found in config/[login to view URL], use [login to view URL] to load your own database gems 31: from /usr/lib/ruby/vendor_ruby/rails/[login to view URL]:in `run' 30: from /usr/lib/ruby/vendor_ruby/rails/[login to view URL]:in `instance_exec' 29: from /usr/lib/ruby/vendor_ruby/rails/[login to view URL]:in `block in <class:Engine>' 28: from /usr/lib/ruby/vendor_ruby/rails/[login to view URL]:in `each' 27: from /usr/lib/ruby/vendor_ruby/rails/[login to view URL]:in `block (2 levels) in <class:Engine>' 26: from /usr/lib/ruby/vendor_ruby/rails/[login to view URL]:in `load_config_initializer' 25: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `instrument' 24: from /usr/lib/ruby/vendor_ruby/rails/[login to view URL]:in `block in load_config_initializer' 23: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `load' 22: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `load_dependency' 21: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `block in load' 20: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `load' 19: from /usr/share/redmine/config/initializers/[login to view URL]:in `<top (required)>' 18: from /usr/share/redmine/config/initializers/[login to view URL]:in `each' 17: from /usr/share/redmine/config/initializers/[login to view URL]:in `block in <top (required)>' 16: from /usr/share/redmine/config/initializers/[login to view URL]:in `eval' 15: from /usr/share/redmine/lib/plugins/acts_as_activity_provider/[login to view URL]:in `block in <top (required)>' 14: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `require' 13: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `load_dependency' 12: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `block in require' 11: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `require' 10: from /usr/lib/ruby/vendor_ruby/active_record/[login to view URL]:in `<top (required)>' 9: from /usr/lib/ruby/vendor_ruby/active_record/[login to view URL]:in `<module:ActiveRecord>' 8: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `run_load_hooks' 7: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `each' 6: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `block in run_load_hooks' 5: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `execute_hook' 4: from /usr/lib/ruby/vendor_ruby/active_support/[login to view URL]:in `instance_eval' 3: from /usr/lib/ruby/vendor_ruby/active_record/[login to view URL]:in `block (2 levels) in <class:Railtie>' 2: from /usr/lib/ruby/vendor_ruby/active_record/[login to view URL]:in `establish_connection' 1: from /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/[login to view URL]:in `spec' /usr/lib/ruby/vendor_ruby/active_record/connection_adapters/[login to view URL]:in `rescue in spec': Specified 'mysql2' for database adapter, but the gem is not loaded. Add `gem 'mysql2'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord). (Gem::LoadError)