A kasuwa na ga sabuwar riga ja.

a is a general locative preposition. Depending on context, it can correspond to English in, at, or on.

In a kasuwa, it means at the market / in the market.
You’ll see it in many similar expressions:

• a gida – at home
• a makaranta – at school
• a ofis – at the office

You might also see a cikin kasuwa, which is more literally inside the market, emphasizing the interior. a kasuwa is the basic, neutral way to say at the market.

Yes, Na ga sabuwar riga ja a kasuwa is also correct.

• Na ga sabuwar riga ja a kasuwa – neutral order: I saw a new red dress at the market.
• A kasuwa na ga sabuwar riga ja – puts the place first: At the market, I saw a new red dress.

Fronting a kasuwa emphasizes the location or sets the scene. The basic meaning is the same; it is mostly about focus and style.

In na ga, na is the 1st person singular subject pronoun in the perfective aspect, so it means I (did).

• na ga – I saw
• na sayi – I bought
• na je – I went

The same form na can also mean of / my, but that is in a different position, between nouns:

• rigar na – my dress
• littafin na – my book

So:

• na ga → I saw (subject pronoun + verb)
• rigar na → my dress (possessive / “of me”)

The basic verb is gani “to see”, but in the simple past/perfective, Hausa normally uses a short stem ga with the subject pronoun:

• na ga – I saw
• ka ga – you (m.sg) saw
• ya ga – he saw

gani is the verbal noun / infinitive (“seeing, to see”). You will meet it in other structures:

• ina ganin shi – I am seeing him / I think so
• na gani (by itself) – I see / I get it (in conversation)

For a normal past statement with an object, na ga sabuwar riga ja is the standard form.

Hausa allows adjectives both before and after the noun, but not in the same way for all adjectives.

1. sabuwar riga

   • sabuwar comes from sabuwa “new” (feminine) in a special pre-nominal form.
   • Many very common adjectives (new, old, big, small, good, bad, etc.) often appear before the noun in these special forms:
     • sabuwar mota – a new car
     • tsohon gida – an old house

2. riga ja

   • Color adjectives like ja “red” much more often follow the noun:
     • riga ja – red dress
     • mota ja – red car

So sabuwar riga ja is built as:

• sabuwar riga – a new dress
• riga ja – a red dress

Combined: sabuwar riga ja – a new red dress.

Both relate to the idea of a “new dress,” but they’re used differently.

• sabuwar riga

  • adjective before the noun in a special form
  • feels like a compact description or classification: a new dress (as a type / newly acquired)
  • very common as a noun phrase on its own.

• riga sabuwa (ce)

  • adjective after the noun; more like a statement about the dress:
    
    • rigar nan sabuwa ce – this dress is new.
  • without ce, riga sabuwa is usually understood in a descriptive or relative sense, but it is less common as a stand‑alone NP meaning just “a new dress”.

For saying “I saw a new dress”, sabuwar riga is the natural choice.

The -r is a linking consonant that appears when certain adjectives (and nouns) come directly before another noun.

Breakdown:

• Base feminine adjective: sabuwa – new (fem.)
• Before a noun: sabuwa + r + riga → sabuwar riga

This -r marks a kind of close connection (a “construct”) between the adjective and the noun. You’ll see the same thing in many pairs:

• farar riga – white dress (from fara “white”, fem.)
• safiyar Lahadi – Sunday morning (from safiya “morning”)

So sabuwar is simply the “before-a-noun” form of sabuwa.

Hausa does not have articles like English a/an or the as separate words.

Indefiniteness is normally unmarked, so sabuwar riga ja can correspond to a new red dress.
Definiteness can be shown in other ways, often by:

• Context
• The -r/-n ending on the noun (rigar / littafin)
• Possessives, demonstratives, etc.

So:

• Na ga sabuwar riga ja – I saw a new red dress.
• Na ga sabuwar rigar ja – I saw the new red dress (more specific/definite).

Yes, you can say rigar ja, but it means something slightly different.

• riga ja

  • normally indefinite: a red dress
  • just noun + adjective.

• rigar ja

  • rigar is the definite/construct form of riga.
  • often understood as the red dress or the dress that is red, especially if you’re contrasting it with other dresses.

In your sentence:

• sabuwar riga ja – a new red dress (indefinite)
• sabuwar rigar ja – the new red dress (more specific, a particular one known in context)

Yes, in principle Hausa adjectives agree in gender and number with the noun, but how you see that agreement depends on the adjective.

• riga is feminine, so “new” in the pre-nominal form appears as sabuwar (feminine), not masculine sabon:

  • sabuwar riga – new dress (fem.)
  • sabon littafi – new book (masc.)

• With ja “red” after the noun in the singular, you don’t see a visible gender change:

  • riga ja – red dress
  • wando ja – red trousers

In the plural, color adjectives do change:

• riguna jajaye – red dresses (plural of ja is jajaye).

So sabuwar clearly shows feminine agreement with riga; ja doesn’t change form here in the singular.

You need to put both the noun and the adjectives in the plural:

• riguna – dresses (plural of riga)
• sababbin – plural pre-nominal form of sabo/sabuwa “new”
• jajaye – plural of ja “red”

So:

• Na ga sababbin riguna jajaye a kasuwa.
  → I saw new red dresses at the market.

For this meaning, you normally do not use na gani with a direct object like that. The natural past form is:

• Na ga sabuwar riga ja a kasuwa. – I saw a new red dress at the market.

As mentioned earlier, gani is the verbal noun (“seeing, to see”), and na gani is often used:

• by itself, meaning I see / I understand, or
• in other constructions like ina ganin…

So for a simple past event with an object, learn and use na ga …, not na gani ….