A German Shepherd dog only really needs a bath once every month which is usually good enough.
That is unless the German Shepherd has fleas and you need to give the German Shepherd a flea bath then you can bathe the German Shepherd more often as in every few days.
Also if the German Shepherd gets muddy or really dirty then you might need to give it a bath more often but just for regular bathing once per month is enough.
Avoid bathing the German Shepherd no more frequently than every 10 days or so as over bathing will strip the German Shepherds coat of it's natural oils.