La transferència immediata arriba avui.

Because transferència is a feminine singular noun in Catalan.

• la = feminine singular definite article
• el = masculine singular definite article

So:

• la transferència
• not el transferència

This is something you usually just learn together with the noun: la transferència.

Because the adjective has to agree with the noun it describes.

Here, immediata describes transferència, which is feminine singular, so the adjective is also feminine singular:

• masculine singular: immediat
• feminine singular: immediata
• masculine plural: immediats
• feminine plural: immediates

So la transferència immediata is correct because both words match in gender and number.

In Catalan, adjectives often come after the noun, much more often than in English.

So:

• transferència immediata = noun + adjective

This is the normal, natural order here. Putting the adjective before the noun would usually sound unusual, poetic, or would change the emphasis.

For a learner, the safest pattern is:

• noun + adjective

unless you specifically learn that a certain adjective often goes before the noun.

Arriba is the 3rd person singular present tense of the verb arribar.

Conjugation:

• jo arribo = I arrive
• tu arribes = you arrive
• ell/ella arriba = he/she/it arrives

In this sentence, the subject is la transferència immediata, which is a singular thing, so Catalan uses arriba.

Catalan often uses the present tense for something happening now, today, or in the near future, especially when it is expected, scheduled, or seen as current.

So arriba avui is a very natural way to say that it arrives today.

This is similar to English sentences like:

• The package arrives today.
• My train leaves tonight.

So even if English sometimes prefers is arriving today or will arrive today, Catalan can very naturally use the simple present.

Avui means today and acts as a time adverb.

Putting it at the end is a very normal word order in Catalan:

• La transferència immediata arriba avui.

Catalan is fairly flexible with adverb placement, but the end position is common and neutral. If you moved avui, the sentence would still usually be understandable, but the emphasis might change.

For example:

• Avui arriba la transferència immediata.
  This puts more focus on today.

The version you were given is straightforward and natural.

No. Avui is used by itself.

You simply say:

• avui = today

So:

• arriba avui
• not arriba en avui
• not arriba a avui

This is similar to English, where you also just say today without a preposition in most cases.

The accent mark in transferència shows where the stress falls and also helps indicate vowel quality.

The stressed syllable is:

• trans-fe-rèn-ci-a

So the stress is not on the first or last syllable; it falls on rèn.

In Catalan, written accents are very important because they help you pronounce words correctly and distinguish between patterns that would otherwise be unclear.

In standard Catalan, rr is a strong rolled or trilled r sound.

So arriba has a stronger r than a single r would have in some positions.

Very roughly:

• arriba sounds like a-REE-ba with a trilled or strongly tapped r

The exact pronunciation can vary somewhat by accent, but the important learner point is that rr is stronger than a simple English r.

Grammatically, Catalan sometimes can place adjectives before nouns, but in this case it would not be the normal everyday wording.

The natural phrase here is:

• la transferència immediata

Putting immediata before the noun would sound marked, literary, or unnatural in ordinary usage.

So for normal Catalan, stick with:

• noun + adjective
• la transferència immediata

Yes. The full noun phrase La transferència immediata is the subject of the verb arriba.

You can break it down like this:

• La = the
• transferència = noun
• immediata = adjective describing the noun
• arriba = verb
• avui = time adverb

So the structure is:

• [Subject] + [Verb] + [Time expression]

That is why the verb is singular: the subject is one transfer.

Usually, no, not in neutral everyday Catalan.

Catalan uses definite articles quite often, and with a specific noun phrase like this, la sounds natural and expected:

• La transferència immediata arriba avui.

Without the article, the sentence would sound odd or incomplete in most contexts. Catalan generally uses articles more consistently than English does in similar cases.