Why do you think your question is about a specific phrase?
OK, you have a sentence that you are trying to translate and understand, and it's the core of your question. Other questions are going to provide similarly a sentence or sentences, if anything to provide a context, an example, or to help understanding what the OP is trying to learn. That doesn't mean that your question needs to be about a specific sentence.
Think: If you were to ask that question, which tags would you use? What is giving you trouble about that question?
Of course, some tags are too general and you could have a hard time figuring out why that sentence does not sound correct to you. Asking for plain translations or corrections in a text is off-topic, of course, but I don't think there are "questions about specific sentences", just questions that don't really clarify what you need to learn.
When you translated the original question to
España es cincuenta trecero más grande país.
How confident are you that that translation is OK? What causes you trouble? The sintax/grammar? Translating the ordinal "fifty third"? The use of articles (that missing "the" that you have in English but you don't in Spanish)?
Bottom line, if you are "I did my best translating but I'm not sure if it goes like that", your question is not about a specific sentence, is a translation attempt or a "are there any mistakes in this text?" question (off-topic).
If you ask specifically about a topic, like, "is the grammar correct"? or "is the use of XYZ correct here?" then is a question about tags/topics XYZ. You could even ask about a particular thing and get a broader answer (or comments) about multiple things that are wrong with your question.
I know that the difference between "are there any mistakes in this text?" and "are there any grammar mistakes in this text?" can be thin or subjective, but actually just yesterday I asked ¿Están los “que” bien usados en esta cita de Napoleón? (or course, it was not my translation attempt) and nobody took it as a a "correct my homework" question.
Just make sure you ask about the things causing you trouble so people can explain the whys of whatever you need to learn in your answer. So when you ask at the end
Is this correct?
Make sure that "this" refers to a specific aspect of the sentence, and not to the whole thing.
If your question was to be closed as off-topic, it's not the end of the world. We have a very friendly site and we discourage people from downvoting post of those who are new to the community.