Fa una hora que la meva mare parla per telèfon.

Yes. Fa is the 3rd person singular form of fer.

In time expressions, Catalan uses fa in a special way:

• Fa una hora = an hour ago
• Fa una hora que ...
  • present tense = ... has been happening for an hour

So in this sentence, fa is part of the pattern fa + time + que + present verb.

Because Catalan normally uses the present tense here for an action that started in the past and is still continuing now.

So:

• Fa una hora que la meva mare parla per telèfon
  means
• My mother has been talking on the phone for an hour

English uses a present perfect continuous form, but Catalan does not need that here. The plain present tense is the normal choice.

It can mean either, depending on the structure.

• Fa una hora by itself usually means an hour ago
• Fa una hora que + present tense means for an hour / has been ... for an hour

So:

• Va arribar fa una hora = He/She arrived an hour ago
• Fa una hora que parla = He/She has been talking for an hour

The que + present verb changes the meaning.

In Catalan, possessives usually go with a definite article:

• la meva mare = my mother
• el meu pare = my father
• la nostra casa = our house

So la meva mare is the normal standard form.

English does not use an article before my, your, our, etc., but Catalan usually does.

Because hora is a feminine noun, so it takes una.

A useful thing to remember: unlike English a/an, Catalan un/una depends on gender, not on sound.

So:

• una hora
• una casa
• un llibre

Even though the h in hora is silent, the word is still feminine, so una is correct.

Because parlar per telèfon is the normal Catalan expression for to talk on the phone / by phone.

Here per expresses the means or channel:

• parlar per telèfon = to speak by phone / on the phone

It is best learned as a fixed expression.

Yes, in this structure it is.

The pattern is:

fa + period of time + que + present tense

So:

• Fa una hora que la meva mare parla per telèfon

If you remove que, the sentence does not work in standard Catalan.

Yes. A very common alternative is:

La meva mare parla per telèfon des de fa una hora.

This also means the same thing.

So you have two very natural patterns:

• Fa una hora que la meva mare parla per telèfon
• La meva mare parla per telèfon des de fa una hora

Both express an action that began in the past and continues now.

You can, but parla is very natural here and usually the more neutral choice.

Catalan often uses the simple present for actions in progress, especially in structures like this one. So:

• Fa una hora que la meva mare parla per telèfon = very natural

You may also hear:

• Fa una hora que la meva mare està parlant per telèfon

That puts a bit more emphasis on the action being in progress right now, but it is not necessary.

Not for this meaning.

If you want to put the duration at the end, you normally need des de fa:

• La meva mare parla per telèfon des de fa una hora

Without des de, fa una hora at the end does not naturally mean for an hour in this context.

So for the intended meaning, use either:

• Fa una hora que ... or
• ... des de fa una hora

No. In Catalan, the h in hora is silent.

So hora begins with a vowel sound, but that does not affect the choice of article the way it does in English. You still say:

• una hora

because the article depends on gender, not on whether the next sound is a vowel.