Eu vou guardar o contrato junto com o comprovante na pasta azul.

Yes, it can be omitted. Portuguese often leaves out subject pronouns because the verb form already shows who is doing the action.

• Eu vou guardar... = natural, with eu stated
• Vou guardar... = also natural, and very common

Including eu can add emphasis, contrast, or clarity.

Vou guardar uses the very common structure ir + infinitive, which expresses a near future or an intended action.

• vou = I go / I am going
• guardar = to keep, store, put away, file, save

So vou guardar is equivalent to I’m going to keep/store/file depending on context.

Portuguese uses definite articles much more often than English. When talking about specific, identifiable things, it is very normal to say:

• o contrato
• o comprovante

Even when English might simply say the contract once and then drop the article in some contexts, Portuguese often keeps it.

Junto com means together with or along with. It emphasizes that the two items will be kept together.

• o contrato junto com o comprovante = the contract together with the receipt/proof document

You could sometimes use just com, but junto com makes the relationship clearer and sounds very natural here.

Comprovante is a very common Brazilian Portuguese word for a document that serves as proof of something. Depending on context, it can mean:

• a receipt
• proof of payment
• a confirmation slip
• supporting documentation

So it is broader than the English word receipt. In Brazil, people often say things like comprovante de pagamento or comprovante de residência.

Yes. In this sentence, pasta means folder, file, or sometimes binder, depending on context. It does not mean the food.

This is an important false friend for English speakers.

Because Portuguese normally contracts em + a into na.

• em + a = na
• em + o = no
• em + as = nas
• em + os = nos

So:

• na pasta azul = in the blue folder

Using em a pasta would sound unnatural.

In Portuguese, adjectives usually come after the noun.

• pasta azul = blue folder
• carro preto = black car
• casa grande = big house

Sometimes adjectives can come before the noun, but after the noun is the default and most neutral position.

Adjectives do agree in gender and number, but not all adjectives have different masculine and feminine forms.

Azul has the same singular form for both masculine and feminine:

• o carro azul
• a pasta azul

Only the plural changes:

• os carros azuis
• as pastas azuis

So pasta azul is correct.

Yes, Portuguese word order is somewhat flexible. The given sentence is natural and clear, but other orders are possible, for example:

• Eu vou guardar o contrato na pasta azul junto com o comprovante.
• Vou guardar o contrato junto com o comprovante na pasta azul.

The original order sounds very normal. The final phrase na pasta azul naturally tells you where the items will be kept.

It depends on context. Guardar is a broad verb and can mean several related things:

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

In this sentence, because of na pasta azul, it sounds like to put away / file / store in the blue folder.