Learn Hardcore Portuguese (Portugal): Na viagem seguinte, a mochileira leva só bagagem de mão e um saco‑cama leve. - On the next trip, the female backpacker takes only hand luggage and a light sleeping bag.

Since viagem is feminine (a viagem), em a viagem must contract to na viagem.
So Na viagem seguinte literally means In the following trip / On the next trip.

Why do we say viagem seguinte and not seguinte viagem?

Adjectives in Portuguese usually go after the noun, so:

viagem seguinte = the following trip

Seguinte viagem is technically possible but sounds odd and very marked; you’d see it mainly in very stylized or poetic language.
For everyday, natural European Portuguese, use viagem seguinte.

What is the difference between seguinte and próxima in this context?

Both can often be translated as next, but there is a nuance:

viagem seguinte = the trip that comes immediately after the one already mentioned (the following trip in a sequence)
próxima viagem = the next trip from now (more from the speaker’s point of view; also more common in speech)

In many contexts they overlap, but seguinte tends to be more tied to a sequence in a narrative, while próxima is more everyday and relative to the present moment.

Why is there a definite article in a mochileira? Could we just say mochileira?

Portuguese uses definite articles much more than English. When you are talking about a specific person already known in the context, you normally use the article:

a mochileira = the backpacker (that one we are talking about)

If you say just mochileira leva só bagagem de mão…, it sounds incomplete or like a title / label, not a normal sentence.
So here a mochileira is the natural form.

Why is it mochileira and not mochileiro?

Mochileiro is the masculine form (male backpacker), and mochileira is the feminine form (female backpacker).
Portuguese nouns referring to people normally agree with the person’s gender:

o mochileiro = male backpacker
a mochileira = female backpacker

The sentence is clearly talking about a woman, so a mochileira is used.

What tense is leva, and why not levou?

Leva is the present indicative, 3rd person singular of levar.
There are two common readings:

Generic / habitual present:
- Na viagem seguinte, a mochileira leva… = On the next trip (whenever that happens in the story), she takes…
Narrative present: present tense used to make the story feel more vivid, instead of past.

You could say Na viagem seguinte, a mochileira levou… (she took) if you want to firmly place it in the past, but the original version is fine and natural in narrative.

What is the difference between leva and traz?

Both come from verbs about carrying things:

levar = to take (away from where the speaker is / to another place)
trazer = to bring (towards where the speaker is)

In this sentence, the focus is on what she takes with her on the trip, so leva is right.
If you were at home and wanted her to bring something to you, you’d use traz (Ela traz a bagagem de mão. = She brings the hand luggage).

What does só mean here, and is its position important?

Here só means only / just:

leva só bagagem de mão e um saco‑cama leve = she takes only hand luggage and a light sleeping bag.

Position:

só leva bagagem de mão (before the verb) usually emphasizes the verb (she only takes hand luggage, she doesn’t do anything else with it).
leva só bagagem de mão (before the object) emphasizes what is limited (she takes only hand luggage, nothing else).

In practice, in this kind of sentence, both positions are often understood the same way, but subtle emphasis can change.

Does só always need the accent? What is the difference between só and so?

In modern spelling, the recommended form is:

só = only, just (adverb)

so without an accent exists mainly in some fixed expressions (like sozinho), not as the adverb only.
So when you mean only, you should write só with an accent.

Why is there no article in só bagagem de mão? Could it be só a bagagem de mão?

Bagagem is often used as an uncountable noun, similar to luggage in English:

só bagagem de mão = only hand luggage (in general, not a specific piece)

If you say só a bagagem de mão, it sounds like you are contrasting the hand luggage with some other specific luggage already known (for example, she leaves the suitcase and only takes the hand luggage we mentioned earlier).
In the neutral, generic sense, só bagagem de mão is more natural.

Is bagagem de mão singular or plural? Can I say bagagens de mão?

Bagagem de mão is grammatically singular, but it usually refers to hand luggage in general, which may include more than one item.

You can say:

bagagem de mão (most common, especially in airline contexts)
bagagens de mão is possible but less frequent; you’d use it if you really want to stress different items or different people’s items, for example:
- As nossas bagagens de mão foram revistadas.

For learners, sticking to the singular bagagem de mão is safe and natural.

Why is it um saco‑cama leve and not um leve saco‑cama?

In Portuguese, descriptive adjectives usually go after the noun:

um saco‑cama leve = a light sleeping bag

Putting leve before the noun (um leve saco‑cama) sounds unusual and a bit literary or stylistic. It can slightly change the feel, sometimes making the adjective more subjective or emotional.
For a neutral description, noun + adjective (saco‑cama leve) is standard.

Why is there a hyphen in saco‑cama? Could I say saco de cama?

Saco‑cama is a compound noun meaning sleeping bag. The hyphen signals that the two parts form a single lexical item with a specific meaning.

saco‑cama = sleeping bag (standard in European Portuguese)
saco de cama would be understood but sounds like a bag for a bed, not the usual term for a sleeping bag.

So in European Portuguese, you normally say saco‑cama.

Why is leve masculine and singular here? How would it change in the plural?

Adjectives agree in gender and number with the noun they refer to:

saco‑cama is masculine singular (um saco‑cama), so we use leve (masculine singular form).

If you had more than one sleeping bag:

dois sacos‑cama leves = two light sleeping bags

The adjective leve has the same form for masculine and feminine in the singular, but it takes an ‑s in the plural (leves).