"Mindenfelől vonatok érkeznek."

Translation: Trains arrive from every direction.

[GerSzej]

I translated from everywhere, this was rejected. Is it incorrect?

[vvsey]

Incorrect in the sense that it is not an exact translation. But the sentence is otherwise valid.

"Mindenfelől" is not a location, it is a directional indicator. The closest translation is probably what is used here, "from every direction".
"Mindenhonnan" is what can be translated as "from everywhere".

Everywhere - mindenhol
From everywhere - mindenhonnan
To everywhere - mindenhova

From every direction - mindenfelől
To every direction - mindenfelé
See, there is no third option here, since I cannot use a direction as a location.

[GerSzej]

Another example of the beauty of Hungarian. Thank you for the explanation.

[Krisbaudi]

Thank you very much! :-)

[GGS1964]

My translation "Trains arrive from all directions" should be accepted, because it has exactly the same meaning.

[jzsuzsi]

There is a report button at the bottom of the screen when you do the lesson. Report "my answer should be accepted" there, that's what it's for.