I completed the sleeves. I took each sleeve and inserted it into the armcye of the dress. The dress is wrong side out while the sleeves are right side out.
I sewed the sleeves in the armcye.
I had a slit for the zipper at the left side of the dress.
I pinned the zipper, starting from the armcye, downwards ...
... and back upwards at the other side. The zipper teeth are aligned with the edge of the slit. I sewed half a centimeter along the slit at the right side.
The neckline's lining is hand-stitched to the dress with an invisible stitch so it couldn't move or stick out.
The petticoat is finished for now. The only thing that's left is the lenght - it must be measured at the fitting.