I have a order field, and a group field
Database is ok, also when i change ordering on site in the grid
But the display gives the wrong order: it orders only on the orderfield

The group is considerated the first ordering. When you reorder the list, you can only reorder in between the groups.
Same, the grouping field must be linked to the ordering group (wizard) if you want it to work well.

> Both 'group by' in the grid, and group key in the ordering wizard.

Do it helps ?