Ni na nema ruwa a gida amma babu.

Yes, both relate to I, but they have different roles:

• ni is an independent pronoun (the full word for I).
• na here is a subject marker attached to the verb (na nema = I searched).

When you use ni na…, you are focusing/emphasizing the subject:

• Na nema ruwa a gida… = I searched for water at home… (neutral).
• Ni na nema ruwa a gida… = It was me who searched for water at home… (maybe not someone else).

So ni is optional and adds emphasis or contrast. Without emphasis, you’d just say Na nema ruwa a gida amma babu.

Na nema is first person singular perfective:

• na = I (subject marker in perfective).
• nema = to search / to look for.

The perfective generally describes a completed action, very often translated with the simple past in English:

• Na nema ruwa = I searched / I looked for water.

Compare:

• Na nema ruwa – I searched (completed).
• Ina nema ruwa – I am searching / I search (ongoing or habitual; progressive/imperfective).

In Hausa, nema already includes the idea of look for / search for. You don’t need an extra preposition such as for:

• English: I looked for water.
• Hausa: Na nema ruwa. (literally: I searched water.)

So nema + direct object expresses look for + object. That’s normal and correct in Hausa.

The usual order in Hausa is:

Subject – Verb – Object – (other information like place, time, manner)

So here:

• Ni / na = subject
• nema = verb
• ruwa = object (what you looked for)
• a gida = location (where)

Hence Na nema ruwa a gida is the natural order.

Putting a gida before ruwa (e.g. Na nema a gida ruwa) would sound wrong or at least very unnatural in standard Hausa. The object normally comes before the place phrase.

a is a general preposition of location. It’s quite flexible and often covers both English in and at, depending on context:

• a gida = in the house / at home
• a kasuwa = in the market / at the market
• a makaranta = in school / at school

So a gida is best understood as “at home” or “in the house” depending on how you translate the whole sentence into natural English. The Hausa preposition a does not make a sharp distinction between in and at the way English does.

Both are correct but slightly different in nuance:

• a gida – at home / at the house (general location).
• a cikin gida – inside the house (more specific: physically inside).

In many contexts they overlap, but:

• Na nema ruwa a gida – I looked for water at home (could include yard, compound, etc.).
• Na nema ruwa a cikin gida – I looked for water inside the house (emphasis on interior space).

Your original sentence uses the more general a gida.

amma is a conjunction meaning but / however.

It functions like English but and links two clauses:

• Na nema ruwa a gida amma babu.
  – I looked for water at home, but there wasn’t any.

Its position is typically at the start of the second clause, just like but in English. You don’t move it around; amma goes right before the clause it introduces.

Babu is an existential/possessive negator, roughly:

• babu = there is no / there isn’t / there wasn’t / there are no / there weren’t.

In your sentence:

• amma babu = but there wasn’t any (implied: water).

The word ruwa is understood from context, so you don’t have to repeat it:

• Longer form: Na nema ruwa a gida amma babu ruwa.
• Natural form: Na nema ruwa a gida amma babu.

This is very common in Hausa. The object after babu is often dropped if it is obvious.

Functionally, babu acts like an existential/possessive negative:

• Babu ruwa. – There is no water.
• Babu kuɗi. – There is no money.
• Babu littafīna. – My book is not there / I don’t have my book.

Hausa does not use a separate verb like to be here. Babu itself carries the idea of “there is not / does not exist / is not available / is not possessed”, depending on context.

So it fills the role that in English would need there is not, doesn’t have, or isn’t any.

Yes. Both are correct:

• Amma babu. – but there wasn’t any (water) – water is implied.
• Amma babu ruwa. – but there wasn’t any water – explicit.

You might choose amma babu ruwa when:

• You want to be extra clear (e.g. in early learner sentences or formal writing).
• You are contrasting kinds of things:
  Akwai abinci amma babu ruwa. – There was food, but there was no water.

In everyday conversation, the shorter amma babu is very natural if the missing thing (here, ruwa) has just been mentioned.

Absolutely. A neutral, very common version is:

• Na nema ruwa a gida amma babu.

This means the same basic thing (I looked for water at home, but there wasn’t any), without the extra emphasis on I. The version with ni:

• Ni na nema ruwa a gida amma babu.

suggests a contrast or emphasis, like:

• I (as opposed to someone else) looked for water at home, but there wasn’t any.

So both are grammatically fine; you choose ni na… when you want that extra focus on the subject.