Why is إِنَّا translated to "indeed we" (Sahih International)? E.g. إِنَّا لِلَّهِ = "Indeed we belong to Allah"

Question

Consider, for example, the following verses:

الَّذِينَ إِذَا أَصَابَتْهُم مُّصِيبَةٌ قَالُوا إِنَّا لِلَّهِ وَإِنَّا إِلَيْهِ رَاجِعُونَ
Who, when disaster strikes them, say, "Indeed we belong to Allah, and indeed to Him we will return."
_{Qur'an 2:156}

فَمَا كَانَ دَعْوَاهُمْ إِذْ جَاءَهُم بَأْسُنَا إِلَّا أَن قَالُوا إِنَّا كُنَّا ظَالِمِينَ
And their declaration when Our punishment came to them was only that they said, "Indeed, we were wrongdoers!"
_{Qur'an 7:5}

Quran.com maps إِنَّا to "indeed we" and وَإِنَّا to "and indeed we" (2:156) and also maps إِنَّا to "indeed we" (7:5). However, this seems to be derived from أنا (ʾanā) meaning "I". Perhaps there's some nuance here I'm unaware of (I'm only just starting on the Arabic alphabet).

Question: Why is إِنَّا translated to "indeed we"?

Answer 1

Arabic pronouns don't really work the same as English ones. In particular, here the word إِنَّا is actually made up of two parts: The emphatic particle إِن meaning "Indeed" and the pronoun suffix ـنا meaning "us".

Ordinarily, this form of pronoun suffix is used for the object of a verb (e.g. Al-Fatihah 6 uses it in اهدنا meaning "Guide us".) or as a possessive on a noun (e.g. Al-'An'Am 23 uses it in ربنا meaning "Our Lord"). Using it as the object of إِن can seem a bit odd to us English folks since "Indeed" really isn't either, but translation can be funny like that sometimes (and "Indeed us…" just sounds stupid. As does "Our indeed…").

The fact that it looks like the subject pronoun أنا meaning "I" is, to the best of my knowledge, purely coincidence.

Answer 2

If you are familiar with Spanish you may realize some similarities between Arabic and Spansih for example:
¡cálmate! includes in one word verb and pronoun these kinds of structure are also present in Arabic language.

The shiddah "ّ " sign in Arabic basically represents a repetition of a letter.

Therefore: إنّا is basically a shorter version of: إننا which stands for إنّ نحن (for an Arabic speaker this sounds a bit weird and incorrect, this is not to be confound with إن نحن as in 14:11) and إنّ is a word that expresses emphasize in the language and in grammar we say it is a word that obligates "Nasb" (a fatha on the verb it was applied on) and is used to emphasize or accentuate حرف نصب وتوكيد, therefore it is legally correct to translate it as indeed, while نحن means we.

إننا is a construct such as cálmate (maybe something like tú cálma tú mísmo but it sounds really weird) in Arabic the last part "نا" refers to a first person plural (or dual plural).