Hi, don't worry about the plastic breaking. This machine is made of very robust plastic, so much so that it can survive being dropped from a great height even.
Anyway, the two pieces in the first pic are the wiring loom cover (black thing) and the round thing is the filter.
The filter goes on the side of the white motor housing, the fluffy side faces the motor and it friction fit around the edges and it will fit in nice and snug once fitted.
You'll need to place the mictoswitch (2nd pic) back into place. It goes at the slot designed for it near where the fat grey wire is sticking out. It's hard to describe but it just pushes in there and the metal sheet thing sticks out. This sticks out so that the cleanerhead activates the switch when in the vacuuming position.
You need to fit the cleanerhead next. It just goes on, self explanatory, the side of the cleanerhead connects with the round thing on the filter side followed by a circlip. But keep the cleanerhead straight because you wanna put it on the other side as well.
Once done, you just screw the moto cover on the bottom.
Now, the black wiring loom cover in the first pic just goes on nextto the small internal hose, it's literally just there to cover the wires. It has one screw hole which corresponds to the one by the internal hose
I hope this helps, it's really hard to explain but hopefully this will help with rebuilding it