The contour map in the link that I provided shows two routes, passing on either side of Gummihorn.
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See attached image- I have numbered the routes as #1 and #2 on a screen grab from that map.
Each starts with a mild climb of about 20 meters to the restaurant. (Do you think in meters, yards, or feet? 20 meters is about 22 yards or 66 feet.). The climb is at an altitude of roughly 2,000 meters ,or about 1 and 1/6 mile high. If you are not used to exercise at that altitude, you may need to take it slowly, although the first part is quite short and can be rewarded by a beer or a coffee at the restaurant..
Then either trail leaves the restaurant as a combined single trail, taking the first turn to the right after about 15 meters, then climbing upwards about 30 meters ( crosses 3 brown lines; the heavier one is the 2000 meter altitude profile line) , then splits into 2 trails at about 2010 meters altitude. After that, each tail roughly parallels the 2000 meter line, and thus is roughly at a steady altitude....with some minor ups and downs. They pass on opposite sides of a small bump of 2067 meters, go around Gummihorn on opposite sides, and get close to TUBA. Then, near the end, after about about 400 meters ( #1) or 500 meters (#2) from the trail split, each trail ascends to Tuba, 2076 meters, for a steep climb of roughly 60 to 70 meters on switchbacks ( wiggly lines on the map) within about 100 meters. That is steep. However, the switchbacks mean that the angle of ascent is a lot less than if you went straight up the slope. They make the climb more gradual.
On that part, fresh from the USA near sea level, I'd have to stop to catch my breath a couple of times.
If you prefer a more gradual climb, take route #2, continue past the ascent to Tuba, and walk another 500 meters, then take a hairpin left. You will then climb from roughly 2000 meters to 2076 meters, spread out over 600 meters of walking, with only a few short steep places. That trail has great views, as well.
Since the total distance from the restaurant on either route 1 or 2 is about 500-600 meters ( 500-650 yards, roughly) it is not a long enough hike to get you in trouble.
I am sure that the trail is rocky, and likely will have some loose gravel. Make sure that you wear sturdy shoes with grippy soles, or preferably, hiking boots with grippy soles, for better ankle support. I find a hiking staff to be very useful on those kinds of trail, and with my sore knees, I must use one. I use it to brace myself if descending on gravel. If you don't have one, you can rent them at the Intersport and other sports stores in the area.
The Männlichen to Kleine Scheidegg trail linked previously is much easier, though longer, and offers a wide range of views ( but, no lakes). Even on that easy trail, there are some short downhill stretches on gravel that need slow going, and a hiking staff is useful. You will note them in the images I posted earlier of my daughter and granddaughter.
Hope for good weather. You don't want to go to that effort if all you can see is clouds.