<<"is it ever possible to lose one's way during hiking in all easy & moderate trails for beginners (e.g. taking the wrong turn in locations where there are no signs)?">>
Check the hiking link that Maria gave you for comments and maps.
It is quite hard to lose your way, because trails are well-marked. But, a map can be very useful when you are deciding between two trails signed to the same destination at a junction, and don't know which trail is steeper or easier. Signage gives times, but not distances....the Swiss don't seem to slow down much on hills. ;-)
In dangerous territory, where a misstep could be a bad ide, a map gives an extra measure of safety.
The Eiger trail is very clear, although the new detour that you noted may not be. (I have not seen it, and read that it was confusing.). Also as noted,
If you are not used to down hill hiking, the total descent of 706 meters, as Maria noted, will not be easuy on your knees. Long level walks help , but the muscles used going down are heavily stressed on that hike. It may be more tiring generally to go up...especially at the mile-high and higher altitude, but the views going down are grand. Going up, as noted, you look at the mountain wall unless you stop and look back.
Going down, you cn finish at Alpiglen( note spelling) and have the famous "Käseschnitte" as a reward.
If your knees are at all troublesome,. Rockoyster's suggestion is an excellent one. That hike has amazing views, and altitude change of only about 160 meters.
And, you can also walk from Kleine Scheidegg down to Alpiglen on the road. Similar good views. "Only" a 447 meter descent.
This topo map has altitudes:
map.geo.admin.ch/?topic=swisstopo&lang=e n&bgLayer=ch.swisstopo .pixelkarte-farbe&catalogNodes=139 2,1538,1396,1430,1436& layers=ch.swisstopo.im ages-swissimage-dop10.metadata,ch.swis stopo.swisstlm3d-wanderwege&layers_visi bility=false,true&E=26 42480.00&N=1159956.88& zoom=7
This explains the color codes:
and, less precisely: