I can't see exactly how your starter works without seeing it apart as there are a few different variations on how part 1 has tension to the centre post but the operating principles are the same.
In the images below the centre bolt is tight in the part 1 of the starter see yellow arrows, there are a couple slits in the plastic and a metal ring clamps the sides together giving tension on the bolt ,if your starter is the same as this but the bolt is loose you may be able to cut some small washers with scissors from an aluminium can and put them in the top of part 1 (orange arrows below) This type of starter won't work if the centre bolt is left loose and not tightened down all the way.Putting washers in may get the starter working if the centre of the starter is loose on the bolt and you can't fix that part.
To check nothing is broken in the starter pawl release part of the starter you can twist part one and the pawls should be ejected out (the green arrows below)
