הם זוג חדש, אבל הם כבר מדברים על מתי להתחתן.

Yes. In the present tense, Hebrew usually does not use a separate word for "am / is / are".

So:

• הם זוג חדש literally looks like they a new couple but it means they are a new couple.

This is completely normal Hebrew. A form of להיות (to be) is usually omitted in the present tense.

Because זוג is a singular noun meaning a pair / a couple.

So Hebrew is structured like:

• they [are] a new couple

Even though the couple contains two people, the noun זוג itself is grammatically singular, just like English a couple is singular in form.

Because חדש describes זוג, not הם.

• זוג = masculine singular noun
• so the adjective must also be masculine singular
• therefore: זוג חדש

Even though the people are plural, the phrase is built around the noun זוג, and that noun is singular.

Hebrew often repeats the subject pronoun in a new clause, especially after words like אבל (but).

So:

• הם זוג חדש, אבל הם כבר מדברים...

is very natural Hebrew.

In English, we also usually repeat the subject:

• They are a new couple, but they are already talking...

So the repetition is normal and expected.

הם is the masculine plural pronoun, and הן is the feminine plural pronoun.

Hebrew uses הם for:

• an all-male group
• a mixed group
• sometimes a group of unspecified gender

So as written, the sentence is either:

• about a male/mixed couple, or
• just using the default masculine plural form.

If the couple were definitely two women, you would normally say:

• הן זוג חדש, אבל הן כבר מדברות על מתי להתחתן.

Notice that זוג חדש stays the same, because זוג is still a masculine singular noun.

מדברים is the masculine plural present-tense form of לדבר (to speak / talk).

It agrees with הם:

• הם מדברים = they are talking

Hebrew present tense is formed with what is historically a participle, so מדברים can mean:

• they talk
• they are talking

The exact meaning depends on context. Here, because of כבר and the situation, it clearly means they are already talking.

כבר means already.

So:

• הם כבר מדברים = they are already talking

It adds the idea that this is happening sooner than one might expect. In this sentence, it suggests:

• they are a new couple,
• but even so,
• they are already discussing marriage timing.

Because Hebrew commonly uses לדבר על to mean to talk about.

So:

• מדברים על = are talking about

Then the topic follows:

• מדברים על מתי להתחתן = talking about when to get married

This is very close to English talk about.

Yes, that is basically the structure.

Hebrew often allows a question word like מתי (when) to introduce this kind of clause after a preposition:

• על מתי להתחתן literally: about when to get married

This is natural Hebrew and corresponds neatly to English:

• talking about when to get married

So even if it feels a little unusual word-for-word, the structure is standard.

להתחתן is the infinitive meaning to get married.

It comes from the verb:

• התחתן = got married
• מתחתן = is getting married / gets married
• להתחתן = to get married

This verb is in the Hitpael pattern, which often has a reflexive or intransitive feel. In practice, להתחתן means to marry / to get married in the sense of entering marriage oneself, not marrying someone else off.

So here:

• מתי להתחתן = when to get married

Usually the most accurate translation is to get married.

That is important because in English:

• to marry someone can be transitive
• to get married is intransitive

Hebrew להתחתן is used for the people entering marriage themselves:

• הם רוצים להתחתן = they want to get married

If you translate it simply as to marry, that is often fine in casual English, but to get married is usually the safer and clearer choice.

A simple transliteration is:

hem zug chadash, aval hem kvar medabrim al matai lehitkhaten

A few pronunciation notes:

• הם = hem
• זוג = zug
• חדש = chadash
  The ח is a throaty sound, like the ch in German Bach.
• אבל = aval
• כבר = kvar
• מדברים = medabrim
• מתי = matai
• להתחתן = lehitkhaten

So the rhythm is roughly:

hem zug cha-DASH, a-VAL hem kvar meda-BRIM al ma-TAI le-hit-kha-TEN