1. At 2 months its very important to not allow GSD pups to grow rapidly, at its limbs will not be able to support the body resulting in bad or down pasterns, or limbs extending outwards from the paws or excessive bending due to strain or bow legs as we say in humans. See to it that it isnt gaining weight rapidly and fat. If not corrected at a early stage will result in permanent damage.
2. Never raise GSD pups on tiled floors.This again causes bad pasterns, limbs extending outwards from the paws.
3.Being maybe a new owner or a first time owner it is better to go by judgement rather than calculations.For instance they shouldnt gett excessive proteins which causes rapid growth, so my advise would be if ur pup looks fat or over weight or growing rapidly reduce the qty of food after consulting ur vet.