Depois da aula, eu quero praticar português ainda mais.

Because Portuguese usually contracts de + a into da.

• de = of, from, after in some expressions
• a = the

So:

• depois de a aula → depois da aula

This kind of contraction is very common:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

So depois da aula is the normal, natural form.

Aula usually means class, lesson, or lecture, depending on context.

In depois da aula, it most naturally means:

• after class
• after the lesson

If the context is school, university, tutoring, or a language lesson, aula is the standard word.

Because Depois da aula is an introductory time expression placed at the beginning of the sentence.

Portuguese often uses a comma after this kind of fronted phrase, especially in writing:

• Depois da aula, eu quero praticar português ainda mais.

You may also see short sentences without the comma in informal writing, but with the comma is clear and standard.

You could absolutely say just:

• Depois da aula, quero praticar português ainda mais.

Portuguese often drops subject pronouns when the verb already makes the subject clear. Since quero clearly means I want, eu is optional.

Including eu can add:

• emphasis
• clarity
• contrast

For example:

• Eu quero praticar português, mas ele quer descansar.

So in your sentence, eu is correct, but not required.

After querer when you mean to want to do something, Portuguese uses the infinitive:

• quero praticar
• quero estudar
• quero falar

This is different from English, which can use both want to practice and sometimes other structures in different cases. In Portuguese, after querer, the normal pattern is:

• querer + infinitive

So eu quero praticar = I want to practice.

Because when talking about a language in a general sense, Portuguese often does not use an article after verbs like falar, estudar, praticar, and aprender.

So these are natural:

• praticar português
• estudar português
• falar português

Using an article here would usually sound less natural in this context.

In Portuguese, names of languages are normally not capitalized.

So:

• português
• inglês
• espanhol

This is different from English, where language names are capitalized.

The accent in português shows the stressed syllable and helps distinguish pronunciation.

• por-tu-GUÊS

The ê tells you that the stressed vowel is there and that it has a closed sound.

Other language names follow a similar pattern:

• inglês
• francês

In writing, the accent is required.

Ainda mais means even more or still more.

In this sentence, it adds the idea that the speaker already wants to practice Portuguese, and wants to do so to a greater extent.

So it gives a sense like:

• more than before
• more intensely
• to an even greater degree

It is a very natural way to strengthen mais.

Yes, mais ainda is possible, but ainda mais is the more common and natural order in many contexts, including this one.

Compare:

• quero praticar português ainda mais = very natural
• quero praticar português mais ainda = also possible, often a bit more emphatic or conversational

For a learner, ainda mais is the safest default choice.

Putting ainda mais at the end is natural because it modifies the idea of praticar português and gives the sentence a smooth rhythm.

Portuguese is flexible, but this order sounds very normal:

• eu quero praticar português ainda mais

Other orders may be possible, but this one is simple and idiomatic.

Both are correct, but they emphasize different things.

• praticar português = to practice Portuguese
• estudar português = to study Portuguese

Praticar suggests active use, such as:

• speaking
• writing
• listening
• conversation practice

Estudar suggests more formal study, such as:

• grammar
• vocabulary
• exercises

So if the speaker means improving through use, praticar is an excellent choice.

Yes, but the tone changes.

• depois da aula = very common, natural, everyday
• após a aula = also correct, but a bit more formal or written

In normal conversation, depois da aula is usually the more common choice.

Usually yes. Depois da aula most naturally suggests after the class or after this class.

Even though English often says just after class, Portuguese commonly uses the article:

• depois da aula

Depending on context, it can refer to the class everyone already knows about.

A broad Brazilian Portuguese pronunciation would sound roughly like this:

• de-POYZ da AW-la, eu KE-ro pra-ti-KAR por-tu-GUES a-IN-da MAIZ

A few helpful notes:

• depois often sounds like depoiz
• eu is often pronounced like a quick ehw / ew
• quero in Brazil usually has an open e sound
• s at the end of mais often sounds like s in many Brazilian accents, though pronunciation can vary by region

This is only an approximation, but it can help an English speaker get oriented.

Yes, to some extent. Portuguese has some flexibility.

For example:

• Depois da aula, eu quero praticar português ainda mais.
• Eu quero praticar português ainda mais depois da aula.

Both are correct, but they have slightly different focus.

• Starting with Depois da aula highlights the time first.
• Putting it at the end makes the main statement come first.

Your original sentence is very natural and clear.