To make a narrow hem of 0.5 cm can be tricky. However, there is a trick to get a professional look. I never press a hemline like this; I always sew the first fold to keep it in place. Here is how I do it.
Fold 0,5 cm and make a stitch along the edge all way round.
Make one more fold and stitch right on top of the first stitch. Then press.