Todavía nos falta comprar el pan para la cena.

Because faltar here does not mean to be absent in the same way as English we are missing. In this structure, faltar means to be still left to do / to remain.

So:

• Nos falta comprar el pan = We still need to buy the bread / Buying the bread is still left for us to do

Grammatically, the thing that is missing or still left is the subject. Here, the subject is the whole action comprar el pan. Since that action is treated as singular, the verb is falta.

By contrast:

• Faltamos would mean something like we are absent or we are missing.

Nos means to us / for us.

In nos falta comprar el pan, the idea is:

• To us, buying the bread is still missing
• more naturally in English: We still need to buy the bread

So nos shows who is affected by what is still left to do.

You could compare:

• Me falta estudiar = I still need to study
• Te falta llamar a tu madre = You still need to call your mother
• Nos falta comprar el pan = We still need to buy the bread

This is a very common pattern in Spanish.

Faltar + infinitive means that an action still remains to be done.

Examples:

• Me falta terminar el trabajo = I still need to finish the work
• Nos falta reservar el hotel = We still need to book the hotel
• Les falta llegar = They still haven’t arrived yet / They still need to arrive

In your sentence:

• Nos falta comprar el pan = Buying the bread is still left for us to do

So the infinitive comprar is acting like a noun phrase: buying the bread.

It is singular because the subject is the infinitive phrase comprar el pan.

In Spanish, an infinitive can function like a singular idea:

• Comprar el pan = buying the bread

Since that whole action is treated as one thing, Spanish uses singular falta.

Compare:

• Nos falta comprar el pan = one action remains
• Nos faltan dos cosas = We still need two things

So if the missing thing is plural, you get faltan:

• Nos faltan el pan y el vino = We still need the bread and the wine

Todavía means still or yet.

Here it adds the idea that this action has not been done up to now:

• Todavía nos falta comprar el pan = We still need to buy the bread

Without todavía, the sentence still works:

• Nos falta comprar el pan

But todavía makes the unfinished status more explicit.

In many cases, todavía and aún are interchangeable:

• Todavía nos falta comprar el pan
• Aún nos falta comprar el pan

Both are natural.

Because after faltar in this structure, Spanish uses the infinitive to name the action that remains.

So:

• comprar = to buy / buying

The sentence is not saying we buy or let’s buy. It is identifying the action that is still pending.

That is why you get:

• Nos falta comprar el pan

and not:

• Nos falta compramos ❌
• Nos falta compremos ❌

Spanish often uses the definite article more than English does.

So comprar el pan is very natural, especially when talking about a specific item needed for a situation, even if English would often just say buy bread.

Compare:

• Tengo que comprar pan = I need to buy bread in general
• Tenemos que comprar el pan para la cena = we need to buy the bread for dinner

In this sentence, el pan sounds like the bread needed for that particular meal.

Para la cena means for dinner.

Para is used here because it expresses purpose or intended use:

• el pan para la cena = the bread for dinner

You are buying the bread for the purpose of dinner.

Por would not sound right here, because por usually expresses ideas like because of, through, by, around, and so on.

So:

• para la cena ✅
• por la cena ❌ in this meaning

In Spain, la cena normally means dinner, usually the evening meal.

So:

• desayuno = breakfast
• comida = lunch / main midday meal
• cena = dinner / evening meal

English supper is not usually the best default translation here.

Yes. There are several natural alternatives, with slightly different tones.

Some common ones are:

• Todavía tenemos que comprar el pan para la cena.
• Aún nos queda comprar el pan para la cena.
• Nos falta por comprar el pan para la cena.

These all mean something close to We still need to buy the bread for dinner.

Small differences:

• tenemos que = more direct: we have to
• nos falta = emphasizes what is still missing
• nos queda = emphasizes what remains left to do
• falta por comprar = also very common; it highlights the pending action

They are related, but not identical.

• Nos falta comprar el pan = We still need to buy the bread
• Nos falta el pan = We are missing the bread / We don’t have the bread

The first focuses on the action that has not been done yet. The second focuses on the thing that is missing.

So if you have not bought it yet, both could make sense depending on what you want to emphasize.

Yes. Spanish word order is flexible, and todavía can often move.

These are all possible, though some are more common than others:

• Todavía nos falta comprar el pan para la cena.
• Nos falta todavía comprar el pan para la cena.
• Nos falta comprar todavía el pan para la cena. (less natural in many contexts)

The first version is the most neutral and natural.

Putting todavía at the beginning is very common because it immediately sets the time idea: still.

Yes, very common.

Spanish often uses faltar to talk about things that are still missing or still left to do. It is a very natural everyday structure.

You will hear things like:

• Me falta llamar al médico.
• Nos falta hacer la compra.
• Te falta estudiar más.
• Todavía me faltan dos páginas.

So this sentence sounds normal and natural in everyday Spanish, including in Spain.