Evitiamo la persona bugiarda.

It can mean either one, depending on context.

• we avoid = evitiamo as the 1st person plural present indicative
• let's avoid = evitiamo as the 1st person plural imperative/subjunctive form used for commands

So Evitiamo la persona bugiarda could mean:

• We avoid the lying person / liar
• Let's avoid the lying person / liar

Only the wider context tells you which meaning is intended.

Because evitare is a direct transitive verb in Italian. It takes a direct object with no preposition.

• evitare qualcuno = to avoid someone
• evitare qualcosa = to avoid something

So:

• Evitiamo la persona bugiarda = literally We avoid / Let's avoid the lying person

English learners sometimes expect a preposition because some verbs work differently across languages, but here Italian is simple: evitare + direct object.

Italian usually needs an article where English may not.

Here la persona means the person, so it sounds like a specific person is being referred to.

Compare:

• la persona bugiarda = the lying person
• una persona bugiarda = a lying person

So if you change la to una, the meaning becomes less specific.

Yes. Persona is a grammatically feminine noun, no matter whether the actual person is male or female.

So you say:

• la persona
• una persona onesta
• una persona bugiarda

even if you are talking about a man.

This is an important difference between grammatical gender and real-life gender. In Italian, adjectives must agree with the noun’s grammatical gender, so because persona is feminine, the adjective must also be feminine.

Because bugiarda agrees with persona, and persona is feminine.

Agreement in Italian means the adjective changes form to match the noun:

• persona bugiarda = feminine singular
• uomo bugiardo = masculine singular
• persone bugiarde = feminine plural
• uomini bugiardi = masculine plural

So bugiarda is not chosen based on whether the person is biologically female; it is chosen because the noun persona is feminine.

Here it is an adjective.

In la persona bugiarda, bugiarda describes persona, so it means lying, dishonest, or a liar-like person.

But bugiardo / bugiarda can also be used as a noun:

• un bugiardo = a liar
• una bugiarda = a female liar

So compare:

• la persona bugiarda = the lying person
• la bugiarda = the female liar

The sentence you have uses the adjective use.

Because in Italian, many descriptive adjectives normally come after the noun, and bugiardo/bugiarda usually does.

So:

• persona bugiarda = normal word order

Putting it before the noun would sound unusual or very marked in most contexts.

For English speakers, this is a common adjustment, because English often puts adjectives before nouns, while Italian often puts them after.

Yes, it is grammatically correct and understandable.

It sounds like you are referring to a specific person who is a liar / dishonest.

Depending on context, native speakers might also say things like:

• la persona che dice bugie = the person who tells lies
• il bugiardo / la bugiarda = the liar
• una persona bugiarda = a lying person

So your sentence is fine, but the most natural alternative depends on whether you want to sound:

• more descriptive: persona bugiarda
• more direct: bugiardo / bugiarda
• more explicit: persona che dice bugie

You would make both the noun and the adjective plural:

• Evitiamo le persone bugiarde.

Changes:

• la → le
• persona → persone
• bugiarda → bugiarde

So:

• la persona bugiarda = the lying person
• le persone bugiarde = the lying people / the dishonest people

Yes, but the meaning changes.

• Evitiamo la persona bugiarda = avoid the lying person, a specific one
• Evitiamo una persona bugiarda = avoid a lying person, any such person

So the choice between la and una depends on whether the person is specific or non-specific.

The main tricky points are:

1. evitiamo can mean we avoid or let's avoid
2. evitare takes a direct object, with no preposition
3. persona is always grammatically feminine
4. the adjective must agree: bugiarda
5. the adjective comes after the noun: persona bugiarda

So even though the sentence is short, it shows several very typical Italian grammar patterns.