La charca estaba llena de moscas, así que mi hermana sacó el repelente del bolso.

Because Spanish normally uses estar with lleno/a de to describe a state or condition.

• estar lleno/a de = to be full of
• So La charca estaba llena de moscas means the pond was full of flies

Using ser here would sound wrong in standard Spanish. Ser is for identity, classification, and more permanent characteristics, while estar is for states and conditions.

Estaba is imperfect because it sets the scene or describes a background situation.

In this sentence:

• La charca estaba llena de moscas = background description
• mi hermana sacó el repelente del bolso = the main action that happened next

This is a very common contrast in Spanish:

• imperfect for description, ongoing situations, background
• preterite for completed actions or events

So the idea is:

• The pond was full of flies
• Because of that, my sister took out the repellent

Sacó is preterite because it refers to a single completed action: she took it out.

• sacó = she took out / got out
• sacaba = she was taking out / used to take out

Here, the sentence tells a specific event that happened in response to the flies, so sacó is the natural choice.

Así que means so, therefore, or so then.

It introduces a consequence:

• La charca estaba llena de moscas, así que...
• The pond was full of flies, so...

It is very common in everyday Spanish.

Compare:

• porque = because
• así que = so

So:

• Había muchas moscas, así que sacó el repelente.
• There were lots of flies, so she took out the repellent.

Because así que introduces the result of the first clause, and in Spanish it is normally separated with a comma in this kind of sentence.

So the structure is:

• situation: La charca estaba llena de moscas
• result: así que mi hermana sacó el repelente del bolso

This punctuation works much like English ..., so ...

Charca usually means a small pond or muddy pool, often natural and not very deep. It can sound a bit more rustic or less formal than estanque.

Roughly:

• charca = pond / pool / muddy pool
• estanque = pond, often man-made or more orderly
• lago = lake

So charca gives a more specific image than just any body of water.

Because llena agrees with la charca, which is feminine singular.

• la charca = feminine singular
• therefore: llena

Agreement in Spanish matters with adjectives:

• El bolso estaba lleno
• La charca estaba llena
• Los bolsos estaban llenos
• Las charcas estaban llenas

Because lleno/a de is the normal pattern in Spanish.

• lleno de agua
• llena de gente
• lleno de moscas

So you should learn it as a chunk:

• estar lleno/a de + noun

English says full of, and Spanish says lleno/a de.

Because after lleno/a de, Spanish often uses a noun without an article when speaking generally.

• llena de moscas = full of flies
• lleno de agua = full of water
• llena de gente = full of people

If you said de las moscas, it would sound more specific, as if you meant the flies already identified in context. Here the sentence just means flies in general.

Here el repelente means insect repellent.

In context, because there are flies, Spanish can simply say el repelente and leave de insectos understood.

But repelente can also be an adjective meaning repellent, off-putting, or even obnoxious in some contexts.

So context matters:

• el repelente = the repellent
• una persona repelente = a very annoying or unpleasant person

Because de + el contracts to del in Spanish.

So:

• de + el bolso → del bolso

This contraction is required in standard Spanish.

The only common exception is when el is part of a proper name, such as:

• de El Escorial

But here el bolso is just a normal noun phrase, so del is correct.

In Spain, bolso usually means a handbag, purse, or a personal bag.

Bolsa more often means a bag in the general sense, especially a shopping bag or plastic bag.

So:

• bolso = handbag / purse
• bolsa = bag

In this sentence, del bolso suggests your sister had the repellent in her handbag or personal bag.

Spanish uses definite articles more often than English.

Here:

• sacó el repelente = she took out the repellent
• del bolso = from the bag/her bag

Even when English might say she took out repellent from her bag, Spanish often prefers the article if the object is identifiable from context.

Also, with body parts, clothing, and personal possessions, Spanish often uses the definite article where English uses a possessive. Here both are possible depending on style, but del bolso is perfectly natural because the bag is understood to be hers from context.

Yes, you could say de su bolso, but del bolso sounds very natural when it is already clear whose bag it is.

Compare:

• mi hermana sacó el repelente del bolso = natural, context makes it obvious it was her bag
• mi hermana sacó el repelente de su bolso = also correct, slightly more explicit

Spanish often avoids possessives when the owner is already obvious.

Not always. Sacar is a very common verb with several meanings depending on context.

Here it means:

• sacar = to take out / pull out

But it can also mean:

• to get: sacar buenas notas
• to remove: sacar la basura
• to bring out
• to obtain

So it is best to learn the core idea of bringing something out / getting something out, and then let context guide the exact translation.

A few useful pronunciation points:

• así has stress on the last syllable: a-SÍ
• que is pronounced roughly like keh
• sacó has stress on the last syllable because of the accent mark: sa-KÓ

The accent marks matter here because they show where the stress goes:

• asi would be incorrect
• saco without an accent is a different form and is stressed differently

Yes. That would also be natural:

• Había muchas moscas, así que mi hermana sacó el repelente del bolso.

This version focuses directly on the existence of lots of flies.

The original:

• La charca estaba llena de moscas

is a bit more descriptive and paints the scene more vividly. Both are correct, but they create slightly different effects.