Mi madre es muy realista: sabe que aprender un idioma lleva tiempo.

Because ser is used for a person’s general qualities or character, while estar is usually used for temporary states or conditions.

So:

• Mi madre es muy realista = my mother is a very realistic person / that is part of her character

Using está realista would sound unusual here, because being realistic is not being treated as a temporary mood.

Here, realista means realistic, practical, or someone who sees things as they really are.

So mi madre es muy realista suggests that she has a sensible, down-to-earth attitude. It does not mean that she is an artist from the realist movement or anything like that in this context.

The colon introduces an explanation of the first idea.

• Mi madre es muy realista:
• sabe que aprender un idioma lleva tiempo.

So the second part explains why the speaker says the mother is realistic.

In English, this works a bit like:

• My mother is very realistic: she knows that learning a language takes time.

You could also write it as two sentences:

• Mi madre es muy realista. Sabe que aprender un idioma lleva tiempo.

Because saber que expresses knowledge or certainty, and that normally takes the indicative, not the subjunctive.

• Sabe que aprender un idioma lleva tiempo = She knows that learning a language takes time

The subjunctive is more common after expressions of doubt, emotion, uncertainty, desire, etc.

Compare:

• Sabe que es difícil = She knows it is difficult
• Duda que sea fácil = She doubts that it is easy

So lleva is in the indicative because the speaker presents it as a fact.

Because aprender un idioma is being used as the subject of the verb lleva.

In English, we often use -ing forms for this:

• Learning a language takes time

In Spanish, it is very common to use the infinitive for this:

• Aprender un idioma lleva tiempo

So:

• aprender = to learn / learning
• aprendiendo = learning, but as a progressive form or adverb-like form, not normally as the subject here
• aprende = he/she learns, which would not fit the structure

Because the whole infinitive phrase aprender un idioma is treated as a single idea, so it takes a singular verb.

• Aprender un idioma = learning a language
• lleva = takes

It works like this in English too:

• Learning a language takes time

Not:

• Learning a language take time

So the singular verb is completely normal here.

Literally, llevar often means to carry or to take, but in this structure llevar tiempo means:

• to take time
• to require time

So:

• Aprender un idioma lleva tiempo = Learning a language takes time

This is a very natural expression in Spanish.

Because llevar tiempo is a common expression meaning to take time in a general sense.

• lleva tiempo = it takes time

This is similar to English, where we also usually say it takes time, not necessarily it takes a time.

You can add words if you want to be more specific:

• lleva mucho tiempo = it takes a lot of time
• lleva bastante tiempo = it takes quite a lot of time
• lleva un tiempo = it takes some time / a certain amount of time

But in the original sentence, the general idea is enough, so tiempo appears without an article.

Because idioma is a masculine noun in Spanish, even though it ends in -a.

So:

• un idioma
• el idioma

This is one of several Greek-origin words that end in -ma and are masculine, such as:

• el problema
• el sistema
• el tema

So un idioma is correct.

Yes. Both are correct, but there is a slight nuance.

• idioma = language
• lengua = language, but also tongue

In many contexts they mean the same thing. However:

• idioma often sounds a bit more like language as a system or foreign language
• lengua can sound a bit more linguistic or formal, depending on context

So:

• Aprender un idioma lleva tiempo
• Aprender una lengua lleva tiempo

Both are fine, but idioma is very natural in everyday speech for learning a language.

Yes, but there is a regional difference.

In Spain, llevar tiempo is very natural and common:

• Aprender un idioma lleva tiempo

In some parts of Latin America, you may also hear:

• Aprender un idioma toma tiempo

That is understandable, but in Spain lleva tiempo usually sounds more natural.

Yes. Spanish allows some flexibility, though the original sentence is very natural.

Original:

• Mi madre es muy realista: sabe que aprender un idioma lleva tiempo.

You could also say:

• Mi madre sabe que aprender un idioma lleva tiempo; es muy realista.
• Mi madre es muy realista porque sabe que aprender un idioma lleva tiempo.

The original version uses the colon to make the second part sound like an explanation of the first.

Yes. Mi madre is a standard, neutral way to say my mother.

A few related options are:

• mi madre = my mother
• mamá = mum / mom, more familiar and personal
• mi mamá = my mum / my mom

So the sentence sounds neutral and natural. If you changed it to mi mamá, it would sound a bit warmer and more informal.

A few natural ways are:

• Mi madre es muy realista: sabe que aprender un idioma lleva mucho tiempo.
• Mi madre es muy realista: sabe que aprender un idioma requiere tiempo.
• Mi madre es muy realista: sabe perfectamente que aprender un idioma lleva tiempo.

These add emphasis:

• mucho tiempo = a lot of time
• requiere tiempo = requires time
• perfectamente = perfectly / very well

But the original sentence is already very natural and clear.

Idioma is pronounced with the stress on o:

• i-dio-ma

In Spanish spelling, if there is no written accent mark, words ending in a vowel, n, or s are normally stressed on the second-to-last syllable. So:

• i-dio-ma

Also, the i at the beginning is pronounced clearly, like:

• ee-dyo-ma approximately for an English speaker

And tiempo is pronounced roughly:

• TYEM-po

The ie in tiempo is a diphthong, pronounced together.