Mis amigos me apoyan cuando hablo español en público, y eso aumenta mi confianza.

Mi and mis both mean my.

• Mi is used with a singular noun:
  
  • mi amigo = my (one) friend
• Mis is used with a plural noun:
  
  • mis amigos = my friends

So in mis amigos, you need mis because you’re talking about more than one friend.

In Spanish, when you talk about a mixed‑gender group, you normally use the masculine plural form.

• All-male group: amigos
• All-female group: amigas
• Mixed group (or gender not specified): amigos

So even if you have male and female friends, mis amigos is the standard form.

Apoyan = they support (3rd person plural, present tense of apoyar)
Me = me (indirect object pronoun, “to me / for me”)

Putting them together:

• Mis amigos me apoyan = My friends support me.

Spanish normally uses an object pronoun like me even if it seems optional in English.
Without me, Mis amigos apoyan just means My friends support, but it doesn’t say who they support.

They’re very different in everyday use:

• Apoyar (a alguien)

  • to support someone (emotionally, morally, sometimes practically)
  • Mis amigos me apoyan. = My friends support me.

• Soportar (a alguien / algo)

  • to put up with, tolerate, stand (often negative)
  • No lo soporto. = I can’t stand him.

So in this sentence, apoyan is correct.
Mis amigos me soportan would sound like “My friends put up with me,” not “They support me.”

Spanish uses the simple present much more often than English for:

• habits
• repeated actions
• general situations

Here, cuando hablo español en público means:

• when(ever) I speak Spanish in public (in general, as a recurring situation)

Cuando estoy hablando español en público would sound more like:

• when I am (in the middle of) speaking Spanish in public (focus on an action in progress)

For a general, repeated situation, cuando hablo is the natural choice.

In context, cuando hablo español en público usually means whenever / every time I speak Spanish in public.

The simple present + cuando often implies a general or habitual situation, not just a single event.

If you wanted to clearly refer to a specific occasion, you’d normally add more context, like:

• Cuando hablo español en público en mi trabajo…
  (When I speak Spanish in public at my job…)

Both forms exist, but usage is different:

• Talking about a language in general, as something you speak, study, learn:

  • Normally without article:
    
    • Hablo español. = I speak Spanish.
    • Estudio español. = I study Spanish.

• Talking about the language as an object or concept:

  • Often with article:
    
    • El español es un idioma muy importante.
      Spanish is a very important language.

So in cuando hablo español en público, you’re just saying “when I speak Spanish,” so no el.

En público literally means in public — in front of other people, not in private.

You can move it in the sentence:

• Mis amigos me apoyan cuando hablo español en público.
• Mis amigos me apoyan cuando, en público, hablo español. (less common, more formal)
• Cuando hablo español en público, mis amigos me apoyan.

The most natural options are the first and the last.
Moving en público to the very beginning (En público, cuando hablo español…) is possible but sounds more stylized.

Spanish demonstratives:

• esto = this (unspecified thing, close to the speaker)
• eso = that (unspecified thing, a bit more distant / something just mentioned)
• aquello = that over there (more distant, often abstract)

When you refer back to a whole previous idea or action, eso is the normal choice:

• Mis amigos me apoyan cuando hablo español en público, y eso aumenta mi confianza.
  = …and that increases my confidence.

Esto here would sound odd; it usually refers to something very immediate, often physically present or about to be explained.

You can say:

• Mis amigos me apoyan cuando hablo español en público, y aumenta mi confianza.

It’s grammatically possible; Spanish can omit the subject when it’s understood.

But:

• It sounds less clear and less natural.
• The listener has to infer that the subject of aumenta is “that (situation).”

Using eso makes it explicit that that (their support) is what increases your confidence, so the original sentence is better style.

Confianza by itself means trust or confidence in general, without saying whose.

• Tengo más confianza. = I have more confidence.
• Tengo más confianza en mis amigos. = I have more trust in my friends.

Mi confianza makes it personal and specific: my confidence.

• …y eso aumenta mi confianza.
  = …and that increases my (personal) confidence.

Both tengo más confianza and aumenta mi confianza are correct in different sentences; here, mi confianza just makes the ownership explicit.

Yes, that’s very natural:

• …y eso aumenta mi confianza.
  = …and that increases my confidence.
• …y eso me da más confianza.
  = …and that gives me more confidence.

Both are correct and common.
Aumenta mi confianza is a bit more neutral/formal;
me da más confianza sounds very idiomatic and everyday.

It’s optional from a purely grammatical point of view, but common and stylistically helpful.

Spanish often omits the comma before y (and):

• Mis amigos me apoyan cuando hablo español en público y eso aumenta mi confianza.

Adding the comma:

• Mis amigos me apoyan cuando hablo español en público, y eso aumenta mi confianza.

makes the two parts feel like slightly more separate clauses, which can improve clarity and rhythm. Both versions are acceptable.