El trato con mis compañeras en clase me ayuda a hablar con más confianza.

Here trato means interaction, contact, or dealings with other people.

So El trato con mis compañeras is not about a business deal. It means something like:

• the interaction with my classmates
• the contact I have with my classmates
• the way I relate to my classmates

In this sentence, trato refers to social interaction.

Spanish often uses the definite article more than English does.

So el trato sounds natural because Spanish treats it as a specific general idea: the interaction / that interaction.

Compare:

• El trato con mis compañeras me ayuda... = natural
• Trato con mis compañeras me ayuda... = not correct here

Even when English might say just interaction with my classmates, Spanish often prefers el trato.

Because the normal pattern is el trato con alguien = interaction/dealings with someone.

So:

• el trato con mis compañeras = my interaction with my classmates

If you changed the preposition, the meaning would change or sound unnatural.

For example:

• trato con alguien = interaction with someone
• el trato de alguien can suggest the treatment from someone or belong to a different structure

So in this sentence, con is the expected preposition.

Because compañeras is the feminine plural form.

That means the speaker is referring to a group of female classmates. If the group were all male, or mixed in standard Spanish, you would normally use compañeros.

So:

• compañeras = female classmates
• compañeros = male classmates, or a mixed group in standard grammar

This does not depend on whether the speaker is male or female. It depends on the people being referred to.

Mis means my.

It is the plural possessive adjective, used before plural nouns:

• mi compañera = my classmate
• mis compañeras = my classmates

A useful point: mis does not change for gender. It only changes for number.

So you get:

• mi compañero
• mi compañera
• mis compañeros
• mis compañeras

En clase means in class or during class.

It tells you the context where the interaction happens.

So:

• con mis compañeras en clase = with my classmates in class

This is a very common expression in Spanish. You often do not need an article:

• Estoy en clase = I’m in class
• Aprendo mucho en clase = I learn a lot in class

Because en clase and de clase mean different things.

• en clase = in class / during class
• de clase = from class / class-related

So:

• mis compañeras de clase = my classmates
• mis compañeras en clase suggests the classmates I interact with in class, or simply places the action in the classroom context

In many situations, compañeras de clase would also be possible, but it would focus more on who they are.
En clase focuses more on where the interaction happens.

Me means me and shows who receives the help.

So:

• me ayuda = helps me

The subject of the verb is the whole phrase:

• El trato con mis compañeras en clase

And that subject helps me do something:

• me ayuda a hablar...

So the structure is:

• [subject] + me ayuda + a + infinitive

Because ayudar is commonly followed by a + infinitive when you say what someone or something helps you do.

Pattern:

• ayudar a + infinitive

Examples:

• Me ayuda a estudiar = It helps me study
• Nos ayuda a entender = It helps us understand
• Me ayuda a hablar con más confianza = It helps me speak with more confidence

So the a is required by the normal structure.

Because con más confianza is the more natural and common way to express this idea.

Spanish often prefers:

• hablar con confianza
• hablar con más seguridad
• hablar con soltura

rather than a formal adverb.

So while a more literal adverb-based expression might exist, hablar con más confianza sounds much more natural in everyday Spanish.

Here confianza means confidence or self-confidence when speaking.

So hablar con más confianza means:

• to speak more confidently
• to speak with greater confidence
• to feel less nervous when speaking

Be careful: confianza can also mean trust in other contexts.
But in this sentence it clearly means self-assurance.

Spanish often leaves the comparison implied.

So con más confianza means:

• with more confidence than before
• with more confidence than I otherwise would
• with more confidence than in other situations

You do not always need to say the second part explicitly. English does this too sometimes.

Yes. This version is natural, but Spanish offers other ways depending on what you want to emphasise.

For example:

• Mis compañeras en clase me ayudan a hablar con más confianza.
  This focuses more directly on the classmates.

• Relacionarme con mis compañeras en clase me ayuda a hablar con más confianza.
  This focuses on the act of interacting with them.

• El trato con mis compañeras de clase me ayuda a hablar con más confianza.
  This sounds very close to the original, but de clase makes it clearer that they are classmates.

The original sentence is fine and emphasises the interaction itself.