Can it be installed on Ionos(1und1) Webspace
This is an Apache with MySQL Database
I think other DB is not Possible
Anyone experiences with this Hoster?
welcome to the Redmine community! :-)
I vaguely presume, you can't. Apache and MySQL would be fine, but I don't think they have support for Rails apps. Since Redmine is based on the Ruby on Rails framework it requires Ruby installed on the server. There aren't many webhosters who support it out of the box. Most of the time they tell you that you have to go the VPS route for that.
If IONOS isn't a hard requirement and you aren't anxious about using a console to SSH into your webspace I'd warmly recommend you to take a look at Uberspace. They support Ruby and also have an excellent description how to install Redmine on your own Uberspace.
I checked with putty and the command
and got: ruby 2.1.5p273 (2014-11-13) [x86_64-linux-gnu]
Do you think it will run?