Ahir vaig guardar el rebut a la bossa, però avui no trobo la llista.

Ahir means yesterday. Catalan often puts a time expression at the beginning of the sentence to set the scene, just like English can do:

• Ahir vaig guardar el rebut... = Yesterday I put away/stored the receipt...

It could also come later, but starting with ahir is very natural.

Vaig guardar is the very common Catalan way to say I stored / I put away / I kept in the past.

It is made of:

• vaig = literally I go, but here it functions as part of the past tense
• guardar = to keep, store, put away

This construction is called the periphrastic past and is extremely common in modern Catalan.

So:

• vaig guardar = I stored / I put away

Even though it looks like I go to store, it does not mean that here.

Catalan often leaves out subject pronouns when they are not needed, because the verb form already shows who the subject is.

• vaig guardar already tells you the subject is I
• trobo already tells you the subject is I

So jo is optional. You would add jo mainly for emphasis or contrast:

• Jo vaig guardar el rebut, però tu no.
  = I put away the receipt, but you didn’t.

In the original sentence, leaving out jo is completely normal.

Guardar can mean several related things, depending on context:

• to keep
• to store
• to put away
• to save

In this sentence, vaig guardar el rebut a la bossa means something like:

• I put the receipt in the bag
• I stored the receipt in the bag
• I put away the receipt in the bag

So yes, it is related to to keep, but here put away or store sounds more natural in English.

El rebut means the receipt.

Catalan uses definite articles very often, sometimes more often than English does. In this sentence, the speaker is talking about a specific receipt, so el is natural.

• el = the for masculine singular nouns
• rebut = receipt

So:

• el rebut = the receipt

In this sentence, a la bossa means in the bag or into the bag, depending on how you interpret the action.

• a often means to, at, or sometimes in/into
• la bossa = the bag

With verbs like guardar, Catalan can use a to indicate where something is put.

So:

• guardar el rebut a la bossa = put/store the receipt in the bag

An English learner may expect something more literally like in the bag, but a la bossa is perfectly natural Catalan here.

Because nouns in Catalan have grammatical gender, and bossa is a feminine noun.

That is why it takes:

• la bossa = the bag

Gender in Catalan does not always match English logic, because English nouns usually do not have grammatical gender. It is something you simply learn with each noun.

Però means but.

The accent mark on ò shows the stressed vowel and helps distinguish pronunciation. Catalan uses accents more systematically than English.

So:

• però = but

It is a very common connector between two contrasting ideas:

• Ahir vaig guardar el rebut..., però avui no trobo la llista.
  = Yesterday I put away the receipt, but today I can’t find the list.

Because the speaker is talking about today, so the second action is happening in the present.

• ahir vaig guardar... = yesterday I put away...
• avui no trobo... = today I can’t find... / today I don’t find...

This shift is completely natural:

• first clause = a completed past action
• second clause = a present situation

So the sentence contrasts what happened yesterday with what is true today.

Trobo comes from trobar, which usually means to find.

• trobo = I find
• no trobo = I don’t find / I can’t find

In natural English, I can’t find is usually the best translation here, even though Catalan literally says I don’t find.

So:

• avui no trobo la llista = today I can’t find the list

In Catalan, standard negation usually places no directly before the verb.

• trobo = I find
• no trobo = I do not find / I can’t find

This is the normal Catalan word order for negation.

Compare:

• Trobo la llista. = I find the list.
• No trobo la llista. = I can’t find the list.

For the same reason as el rebut: Catalan often uses the definite article when talking about a specific thing.

• la = the for feminine singular nouns
• llista = list

So:

• la llista = the list

Using the article is very natural here because the speaker has a specific list in mind.

Because Catalan articles change according to grammatical gender.

• el = masculine singular
• la = feminine singular

In this sentence:

• el rebut = the receipt
• la bossa = the bag
• la llista = the list

This is one of the first things English speakers need to get used to in Catalan.

The word order is very natural and straightforward for Catalan:

• Ahir = time expression
• vaig guardar = verb
• el rebut = direct object
• a la bossa = place
• però = connector
• avui = time expression
• no trobo = negative verb
• la llista = direct object

Catalan often follows a pattern similar to English, especially in simple sentences, so this sentence is not unusually arranged.

A broad pronunciation guide would be:

• Ahir ≈ uh-EER
• vaig guardar ≈ vatch gwar-DAR
• el rebut ≈ el ruh-BOOT
• a la bossa ≈ uh luh BO-suh
• però ≈ peh-RO
• avui ≈ uh-VWEE
• no trobo ≈ no TRO-bu
• la llista ≈ luh YEES-tuh or luh LYEES-tuh, depending on accent

Exact pronunciation varies by dialect, but this gives an English speaker a rough idea.