Translation:Kékestető is high whereas Lake Balaton is deep.
I don't see the Hungarian word for "lake" anywhere in the Hungarian question. I know this is only a technicality because "Balaton" obviously means the lake here. However, Balaton is more than a lake. It's a place, and even a region.
"Tall" is OK here. I think it's mostly a matter of personal preference. Not that this is a perfect gauge of such things, but "tallest mountain" and "highest mountain" both get about the same number of Google results, and there are plenty of examples of fluent English speakers and writers using both.
It would be good for the exercise to accept both words, though, so it's worth reporting if you get the chance.
I agree high should be accepted too. Tall works too, but mountains can be high as well.
Eather there is no English word for " tető". I guess it should be something like "Kékes top".
"Kékes summit" would sound nice. Or "peak". But I guess the addition of tető is made so that you know you're talking about the mountain and not the colour.
Isn't Kékestető the actual name of the mountain (or region), but most people call it Kékes?