El meu nebot i jo hem agafat el metro fins a l'última parada de la línia verda.

Because the subject is El meu nebot i jo = my nephew and I, which means we.

So Catalan uses the 1st person plural auxiliary:

• jo he agafat = I have taken
• tu has agafat = you have taken
• ell/ella ha agafat = he/she has taken
• nosaltres hem agafat = we have taken

Since my nephew and I = nosaltres, the correct form is hem agafat.

Here agafar means to take in the sense of taking transport.

So:

• agafar el metro = to take the metro
• agafar l’autobús = to take the bus
• agafar un tren = to take a train

It can also mean to grab, to catch, or to pick up, depending on context. It is a very common verb in Catalan.

Both are understandable, but El meu nebot i jo is usually more natural and polite, because speakers often mention themselves last.

This is similar to English preferring my nephew and I over I and my nephew.

So:

• El meu nebot i jo = natural
• Jo i el meu nebot = possible, but less elegant in many contexts

In Catalan, possessives are usually used together with a definite article.

So Catalan normally says:

• el meu nebot = my nephew
• la meva germana = my sister
• el teu amic = your friend

This is different from English, where you normally just say my nephew without the.

Fins a means as far as / up to / until when followed by a destination or endpoint.

So:

• fins a l’última parada = up to the last stop
• fins a Barcelona = as far as Barcelona

You will sometimes see just fins, but fins a is very common and standard before places or endpoints.

Because la becomes l’ before a vowel sound.

The full form would be:

• la última parada

But Catalan normally contracts it before a vowel:

• l’última parada

Other examples:

• l’estació
• l’amiga
• l’illa

This works much like French apostrophes in forms such as l’école.

Because última agrees with parada, which is a feminine noun.

• la parada = feminine
• therefore: l’última parada

If the noun were masculine, you would use últim:

• l’últim tren = the last train

So this is just adjective agreement:

• masculine singular: últim
• feminine singular: última

Because verda describes línia, and línia is feminine.

• la línia = feminine
• so: la línia verda

Compare:

• el cotxe verd = the green car
• la línia verda = the green line

Again, this is normal adjective agreement in Catalan.

This means of the green line or, more naturally in English, on the green line.

Literally:

• la parada de la línia verda = the stop of the green line

Catalan often uses de in places where English may prefer of, for, or on, depending on the context.

So in natural English, the whole part would be:

• the last stop on the green line

even though Catalan literally says something closer to the last stop of the green line.

Yes, in many contexts vam agafar would also be possible.

Catalan has two very common past forms here:

• hem agafat = present perfect
• vam agafar = simple past expressed with the periphrastic form

Very roughly:

• hem agafat often feels connected to the present or to a time period that still includes now
• vam agafar often presents the action as a finished past event

In real usage, especially depending on region and context, there can be overlap. So a learner may hear both.

Yes, it is normally el metro.

So you say:

• el metro
• agafar el metro
• anar amb metro or anar en metro in some contexts

Like many nouns, its gender simply has to be learned with the word.

You would need to change both the noun and the possessive form:

• El meu nebot i jo... = My nephew and I...
• La meva neboda i jo... = My niece and I...

Notice the changes:

• nebot → neboda
• el meu → la meva

That is because neboda is feminine.

Línia is pronounced roughly like LEE-nee-uh, with the stress on the first syllable.

The written accent in lí- shows where the stress falls:

• línia

Without getting too technical, the accent mark helps show that the word is stressed differently from what you might otherwise expect.

So the stress is:

• LÍ-ni-a

not on the middle or last part.

Yes, in this sentence l’última parada means the last stop, and depending on context it can refer to the final stop or terminus of the line.

A very common transport phrase is:

• fins a l’última parada = to the last stop

So if someone rode the metro all the way to the end of the line, this is a natural way to say it.