Nail scissors or nail klipser can cause fine cracks on the nail. At best, you reduce file your nails with a nail. Nail files made of glass or sand sheet are, in principle, than files made of metal.
It may happen that the nails are too thick to cut effectively with a file. In this case, you can use a nail clipper. There are also robust versions for particularly “stubborn” cases. Treat your feet before a foot bath – it softens the nails and makes it easier to Cut.
Nails should be kept short. Long nails break more easily, splinters, and so can make for injuries.