The two planning numbers in the mountains: elevation gain drives effort more than distance, and the times on yellow signposts are pure walking time — breaks not included.
Kilometres tell you almost nothing in the mountains. For roughly 1,200 metres of ascent, budget about four hours of pure walking time — for eight flat kilometres, only about two. That gap is where most first tours go wrong: the distance sounded harmless, the elevation profile wasn't. As a beginner you're well served by 300 to 500 metres of ascent, which is about an hour to ninety minutes of climbing. The second thing people miss: the time on a yellow signpost is pure walking time — no breaks, no photo stops, no hut lunch. Add a generous margin on top, or you'll be racing the light at the end — and the descent in fading light is exactly where most accidents happen.