Mia nonna sa cucire molto bene.

In Italian, with many singular close family members, the definite article is often dropped before the possessive.

So you usually say:

• mia nonna = my grandmother
• mio padre = my father
• tua sorella = your sister

Instead of:

• la mia nonna
• il mio padre
• la tua sorella

A few important notes:

• This usually applies to singular family nouns.
• It often does not apply to plurals:
  • i miei nonni = my grandparents
• It also often does not apply when the family noun is modified:
  • la mia nonna italiana
  • la mia cara nonna
• Some forms like loro behave differently:
  • la loro nonna

So mia nonna is the normal, natural choice here.

Sa is the third-person singular form of sapere.

In this sentence:

• mia nonna = my grandmother
• sa = knows how
• cucire = to sew

So sa cucire means knows how to sew or simply can sew.

This is a very common Italian pattern:

• so nuotare = I know how to swim
• sai guidare? = do you know how to drive?
• Maria sa cantare = Maria can sing / knows how to sing

Here, sapere + infinitive expresses having the skill or know-how to do something.

Because sapere + infinitive usually means to know how to do something, while potere + infinitive usually means to be able to / to be allowed to / to have the possibility to do something.

Compare:

• Mia nonna sa cucire. = My grandmother knows how to sew.
  
  • This focuses on skill.
• Mia nonna può cucire. = My grandmother can sew.
  
  • This could mean she is able to right now, or that circumstances allow it.

So if you want to say someone has learned a skill, sapere is often the best choice.

Because after sapere in this meaning, Italian uses the infinitive of the action.

Pattern:

• sapere + infinitive

Examples:

• sa parlare italiano = he/she knows how to speak Italian
• sanno ballare = they know how to dance
• so cucinare = I know how to cook

So in sa cucire, the verb cucire stays in its base form, to sew.

Molto bene means very well.

Here is how it works:

• bene = well
• molto = very

So:

• cucire bene = to sew well
• cucire molto bene = to sew very well

Italian often builds adverbs this way:

• parla bene = he/she speaks well
• parla molto bene = he/she speaks very well
• canta abbastanza bene = he/she sings quite well

So molto strengthens bene.

Because bene is an adverb, while buono is an adjective.

You need an adverb here because it describes how she sews.

• bene = well
• buono / buona = good

Compare:

• Mia nonna sa cucire molto bene. = My grandmother sews very well.
  
  • bene describes the action
• Mia nonna è molto brava. = My grandmother is very good.
  
  • here you describe the person
• È una buona sarta. = She is a good seamstress.
  
  • buona describes the noun sarta

English also does this contrast:

• She sews well
• She is good

Yes. In many contexts, sa cucire can naturally translate as can sew.

Literal structure:

• sa = knows
• cucire = to sew

But natural English often prefers:

• My grandmother can sew very well

Still, the Italian specifically emphasizes know-how / skill, not just possibility.

So depending on context, these can all work:

• My grandmother knows how to sew very well
• My grandmother can sew very well
• My grandmother is very good at sewing

The normal word order here is:

• Mia nonna sa cucire molto bene.

This is the most neutral and natural order.

You can sometimes move things for emphasis, but the basic structure is:

• subject + verb + infinitive + adverb

Examples:

• Mia nonna sa cucire bene.
• Mia nonna sa cucire molto bene.

You might also hear emphasis like:

• Mia nonna sa cucire bene, molto bene.

But for a learner, the original order is the one to remember.

A few pronunciation points help here:

• cucire is pronounced roughly koo-CHEE-reh
• the ci in cucire sounds like chee
• sa is a simple sah

So sa cucire sounds roughly like:

• sah koo-CHEE-reh

Also note:

• Italian pronunciation is usually very regular.
• The stress in cucire falls on the -ci- syllable: cu-CI-re

Yes. Mia nonna cuce molto bene is also correct, but it means something slightly different in focus.

• Mia nonna sa cucire molto bene = My grandmother knows how to sew very well / can sew very well
  
  • emphasizes skill or ability
• Mia nonna cuce molto bene = My grandmother sews very well
  
  • states what she does / how well she does it

Both are natural. The sentence with sa cucire highlights that sewing is a skill she has.

Cucire is an -ire verb, meaning to sew.

Its basic infinitive form ends in -ire, like:

• dormire = to sleep
• aprire = to open
• sentire = to hear

Its present-tense form for he/she is:

• cuce = he/she sews

So:

• mia nonna cuce = my grandmother sews

In your sentence, though, it stays in the infinitive because it follows sa:

• sa cucire = knows how to sew