"The Belgian doctors are walking down from the hill, too, from which we are."
Translation:A belga orvosok is arról a hegyről sétálnak le, amelyikről mi.
Is is pretty easy. It needs to come right after the thing you're "also"-ing. So this sentence with A belga orvosok is is saying it's not just us walking down, but "the belgian doctors, too."
The English translation is a mess partly because it can be harder to figure out where to put the word "too" in English, and they didn't figure it out correctly.
Usually, you can put the English "too" right after the same phrase it came after in the Hungarian, with commas, and it'll work although it may not be the smoothest.
So, you'd get: "The Belgian doctors, too, are walking down the hill from which we are [walking down]."
In order to get this right going from English to Hungarian, you'd have to reason out that that is what the English sentence was supposed to mean.