Translation:The Margaret island is the first stop from the bridge.
Yes, Margaret Island should not receive an article here (since it's a proper name). I think it should also accept it untranslated, as Margritsziget. That's how I usually refer to it in English conversations in Budapest, anyway.
I think that "Margit Island" is a proper translation into English. It is a name, and names do not translate. You do not say Louis Kossuth, just because "Louis" is the translation of "Lajos".
So, is this sentence putting more emphasis on the bridge than the island? I feel as if it is based on the way it is structured
If I were to ask if Margitsziget was the first stop from the bridge, would it then be structured "A Margitsziget az első megálló a hídtól?"?
Yes, that's right, but because the verb is only implied here, the emphasis isn't strong. Which word you stress in speech is also important. If you ask "A hídtól az első megálló a Margitsziget?" while stressing "Margitsziget", it means exactly the same as your question. Conversely, if you stress "első" in your question, you ask if it's the first stop from the bridge.
In the DL English, the 'the' should not be used (even though Hungarian uses the 'a'). So, they don't mean the stop, they just made a mistake in the English, because Hungarian takes the definite article in these situations and English does not.
So they actually mean "Margaret Island is the first stop after the bridge."
Yes, except literally here "from" rather than "after". (Either is OK English.)
"The Margaret island is the first stop from the bridge."
No, no, no, no. This English is just plain wrong.
Frustratingly, I cannot report it, as using correct English is accepted, and none of the reporting options cover this case.
"From the bridge, the first stop is Margaret Island" is correct English. That what is listed above is not.
(1) Why was I wrong to have written, " From the bridge the first stop is Margaret Island" and the reason I translated Margitsziget is because I was marked wrong for NOT translating Kati as Kathy just yesterday. (2) AND why is my word order wrong? Since there was no question to give us context for the answer I don't understand how anyone can argue for any particular correct word order. Any answers?
Your word order and translation is perfectly fine in English. In fact, this is how I naturally translate it myself. It looks like this translation is no longer marked as an error.