Translation:I ate the porridge right away, and the orange an hour later.
It's a bit semantically awkward. Usually "in an hour" is either used with the future (as discussed) to specify a time: "I will help you in an hour", or to indicate how long the activity will take: "He did it in an hour". If you mix these you can create ambiguity, such as: "I can do it in an hour". What's meant is sometimes clear from context, but not always.
Your sentence would be better if you said "...after an hour". It seems to me через can be translated with either "in" or "after", but in this case the latter is better.
i think your suggestion highlights why "i ate the porridge right away and the orange in an hour" is not only awkward, but probably wrong! If "i ate the porridge right away and the orange one hour later", then i would understand this as both having taken place in the past (e.g. porridge 2 hours ago and apple 1 hour ago). But "in an hour" is in my understanding used for something which will happen in the future (e.g. porridge 6 minutes ago, apple in one hour). But the Russian sentence has only one verb, and it is in the past tense. And maybe worth noting the verb isn't only in past tense, but perfective as well.
I'll reply here so the indenting doesn't get out of control. «после» is "after" in the sense of "the period of time after something", e.g. "«после час» is "after one o'clock". «через» is "after" in the sense "after the specified period has elapsed, starting from now unless specified", so «через час» is "an hour from now". English uses the same word for both concepts; Russian does not. Wiktionary has a good example: «че́рез семь мину́т по́сле отхо́да» = "seven minutes after departure".
Wiktionary is an excellent resource:
Would a native speaker care to comment?
I had the word cloud thing, and "and an hour later the orange" was not accepted. It is correct: if I would actually write it, it would be "and, an hour later, the orange", or instead of commas perhaps em dashes. This kind of construction is perfectly fine in speech.
(Recovered comments) 1: Straight away and right away - is there any differences?
2 AndroidKanada: Not in meaning: "straight away" is British, "right away" is American.
Not to be confused with the noun "straightaway" of course. ( Or a right-of-way. (
1: Thank you, friend.
BTW, my Yandex translator doesn't know the noun "straightaway". What is the difference between "straight away" and "straightaway"?
2 AndroidKanada: A straightaway is a straight section of a race course.
П.С. The British will sometimes spell the adverb phrase without the blank: "I will answer straightaway." But context should make it clear which it is.
1: Thank you, I got it.