Klingelton lauter geht nicht

I think all of us have felt this pain.
IIRC 3d max is more for 3d graphics than 3d printing
Blender is arguably the best all around 3d program but has a huge learning curve.
Itis open source. So no charge but donations encouraged.
Mesh mixer and netfabb basic are both free programs to fix stl files.
Sometimes  cura will slice files that slicer will not.
As far as programs that will check files an show the errors blender will do this . Some folks will create a file with something like sculptris and then tune in blender.
What are you designing ??

123d Design is probably the easiest and best basic deign program for geometric/mechanical type designs.
Sculptris is a good beginner program for organic sculpting.

There is no one answer and no one tool that fits all . Sometimes different tools or several tools on the same job.
Depending on the file it is sometimes faster to just redraw with something like sketchup or 123d than to repair.

Hope this helps .
tin