Si llegamos tarde a la pastelería, quizá no quede otra tarta para el cumpleaños.

After si for a real or possible future condition in Spanish, you normally use the present indicative, not the subjunctive.

So:

• Si llegamos tarde... = If we arrive late...

This is the standard pattern for likely conditions:

• Si tengo tiempo, voy.
• Si hace buen tiempo, salimos.

English often uses a present form here too: If we arrive late..., not If we will arrive late...

You would not say si lleguemos in this kind of sentence.

Quede is the present subjunctive of quedar.

It appears here because quizá expresses doubt or possibility, and the speaker is not presenting the result as a fact. So:

• quizá no quede otra tarta = maybe there won’t be another cake left

With quizá / quizás, both indicative and subjunctive are possible:

• Quizá no queda otra tarta → sounds more factual or more confident
• Quizá no quede otra tarta → sounds more uncertain or tentative

In this sentence, the subjunctive fits well because the speaker is guessing about a possible future situation.

Here, quedar means to remain, to be left, or to still be available.

So:

• no quede otra tarta = there may not be another cake left

This is a very common use of quedar when talking about stock, food, time, seats, and so on:

• No queda pan. = There’s no bread left.
• ¿Quedan entradas? = Are there any tickets left?

So in this sentence, it does not mean to stay or to meet up.

Otra means another or one more.

So otra tarta means:

• another cake
• one more cake

In context, the idea is that if they arrive late, there might not be any additional cake left to buy for the birthday.

Spanish often uses otro / otra where English might sometimes say another or even any other depending on context.

Because the sentence is talking about a possible future result, not a present fact.

• No hay otra tarta = There isn’t another cake
• No quede otra tarta = there may not be another cake left

The second one fits the idea of uncertainty after arriving late.

Also, quedar is especially natural when talking about what remains after other people may have bought something.

Because llegar normally takes a when it means to arrive at a place.

• llegar a la pastelería = to arrive at the cake shop / pastry shop

So:

• Si llegamos tarde a la pastelería... = If we arrive late at the cake shop...

Using en would not be the normal choice with llegar in this structure.

In Spain, pastelería usually means a cake shop or pastry shop.

It is the place where you buy:

• cakes
• pastries
• tarts
• sweets

That fits well with tarta.

A learner might compare it with panadería:

• panadería = bakery, mainly bread
• pastelería = pastry/cake shop

In real life, one shop can sometimes be both.

In Spain, tarta is very common for a whole cake, especially a celebration cake such as a birthday cake.

So:

• tarta de cumpleaños = birthday cake

In some other Spanish-speaking countries, pastel is more common for cake. But since this is Spanish from Spain, tarta sounds very natural.

Para here shows purpose or intended use.

• una tarta para el cumpleaños = a cake for the birthday

It means the cake is intended for that occasion.

If you said del cumpleaños, that would sound more like of the birthday or belonging to the birthday, which is not the normal idea here.

So para is the natural preposition.

Yes. Quizá and quizás both mean maybe or perhaps.

Both are correct, and the difference is mainly stylistic or regional preference. In this sentence, either would work:

• Quizá no quede otra tarta
• Quizás no quede otra tarta

Both are common.

Here it means late.

That is because it goes with llegamos:

• llegar tarde = to arrive late

So:

• Si llegamos tarde... = If we arrive late...

It does not mean in the afternoon here. To mean in the afternoon, the context would be different, such as:

• por la tarde = in the afternoon

Yes, but the current version is very natural.

Spanish often uses the present indicative after si even when referring to the future:

• Si llegamos tarde... = If we arrive late...

And then the second part can stay tentative with quizá + subjunctive:

• quizá no quede otra tarta

You could also hear other versions depending on how certain the speaker feels, but this sentence is a very good, natural way to express the idea.