Hike from Berggasthaus First, which is north of Grindelwald, to Berghaus Baregg, which is south of Grindelwald. The "first half" of the hike, going down to Grindelwald, is covered by the AllTrails map in the first link, but the AllTrails hike is in the reverse direction. The "second half" of the hike, continuing south and up the mountain, is covered by the AllTrails map in the second link. This is a long day, so you might want to ride the gondolas down to Grindelwald. That cuts out half the walking distance, but you will still have the 900 meter climb up to Berhhaus Baregg.