Wir verhalten uns freundlich.

No. The full verb here is sich verhalten, which means to behave or to conduct oneself.

Even though it contains halten, you should learn it as its own verb, not as plain halten with an extra piece added. In this sentence:

• wir verhalten uns = we behave / we conduct ourselves

So Wir verhalten uns freundlich means that we behave in a friendly way.

Because sich verhalten is a reflexive verb. In German, many verbs are used with a reflexive pronoun, and this is one of them.

The reflexive pronoun changes with the subject:

• ich verhalte mich
• du verhältst dich
• er/sie/es verhält sich
• wir verhalten uns
• ihr verhaltet euch
• sie/Sie verhalten sich

So with wir, the reflexive pronoun is uns.

No. In this meaning, verhalten is inseparable.

That means the prefix ver- stays attached to the verb and does not move to the end of the sentence.

So you say:

• Wir verhalten uns freundlich.

not:

• Wir halten uns freundlich ver.

In the perfect tense, it also stays together and does not add ge-:

• Wir haben uns freundlich verhalten.

Because here freundlich is not directly describing a noun. It describes how the action is done, so it functions like an adverb in English.

German often uses the plain adjective form for this:

• ein freundlicher Mensch = a friendly person
  Here it describes a noun, so it gets an ending.
• Wir verhalten uns freundlich = We behave in a friendly way
  Here it describes the verb, so there is no ending.

So English often uses -ly, but German usually does not.

You can think of it as an adjectival form used adverbially.

In practical terms, the important point is this:

• German does not usually have a special -ly ending like English.
• The same basic form often does both jobs.

So freundlich can mean:

• friendly before a noun, with endings: eine freundliche Frau
• in a friendly way after a verb: Sie spricht freundlich

That is exactly what happens in Wir verhalten uns freundlich.

Because in a normal German main clause, the finite verb goes in second position.

Here the structure is:

• Wir = subject
• verhalten = finite verb
• uns = reflexive pronoun
• freundlich = adverbial description of manner

So the sentence follows a very normal German pattern.

If you add more words, the order can shift a bit, for example:

• Wir verhalten uns immer freundlich.
• Heute verhalten wir uns freundlich.

But in a simple statement like this, Wir verhalten uns freundlich is the natural order.

Not quite.

• Wir sind freundlich describes what we are like: our character, general quality, or current state.
• Wir verhalten uns freundlich describes our behavior: how we are acting.

So sich freundlich verhalten focuses more on conduct in a situation.

For example, someone might not be a particularly warm person in general, but in a certain situation they still behave politely and kindly. In that case, sich freundlich verhalten fits especially well.

Yes, that is understandable, but it has a slightly different feel.

• sich verhalten is fairly neutral and can sound a bit more formal.
• sich benehmen is also to behave, but it often has more to do with manners or proper/improper behavior.

So:

• Wir verhalten uns freundlich = neutral, natural, slightly more formal
• Wir benehmen uns freundlich = possible, but less neutral in some contexts

Learners often hear sich benehmen in sentences like:

• Benimm dich! = Behave yourself!

In the perfect tense, it becomes:

• Wir haben uns freundlich verhalten. = We behaved in a friendly way.

A few other useful forms are:

• Ich verhalte mich freundlich.
• Du verhältst dich freundlich.
• Sie verhalten sich freundlich.

Notice again that the reflexive pronoun changes with the subject, but freundlich stays the same.