Después de haber preparado el esquema, me sentí tan seguro que pude exponer sin ponerme nervioso.

Both are possible, but they are not exactly the same.

• Después de preparar el esquema = after preparing the outline
• Después de haber preparado el esquema = after having prepared the outline

Using haber + past participle emphasizes that the preparation was fully completed before the next action happened. It is a more explicit way to show sequence.

In everyday Spanish, many speakers would also say Después de preparar el esquema..., especially in conversation. The version with haber preparado sounds a bit more precise or formal.

In this context, el esquema usually means an outline, plan, or structured summary of what someone is going to say.

In Spain, esquema is very common in academic and presentation contexts. It often refers to notes arranged in a clear, organized way rather than a full script.

So here it suggests the speaker prepared a clear outline before presenting.

Because the verb here is sentirse, which means to feel in the sense of to feel a certain way.

• Sentí frío = I felt cold
• Me sentí seguro = I felt confident / I felt sure of myself

The pronoun me is part of the reflexive verb sentirse. Without it, sentí usually means I felt something directly, like a sensation or emotion as an object.

So:

• Sentí miedo = I felt fear
• Me sentí seguro = I felt confident

Here seguro means confident or sure of oneself, not safe.

So me sentí tan seguro means:

• I felt so confident
• or I felt so sure of myself

Spanish often uses seguro where English would prefer confident.

Tan ... que means so ... that.

In this sentence:

• tan seguro que pude exponer...
• so confident that I was able to present...

This structure is very common in Spanish:

• Estaba tan cansado que me dormí. = I was so tired that I fell asleep.
• Habló tan rápido que no entendí nada. = He spoke so fast that I understood nothing.

So tan goes before an adjective or adverb, and que introduces the result.

Because pude focuses on a completed achievement: the speaker managed to do it.

• Pude exponer = I was able to present / I managed to present
• Podía exponer = I could present / I was capable of presenting

In this sentence, the speaker is talking about a specific occasion, and the idea is that their confidence allowed them to actually succeed in giving the presentation. That makes pude the natural choice.

A useful contrast:

• Podía hacerlo = I was able to do it / I had the ability to do it
• Pude hacerlo = I managed to do it / I succeeded in doing it

No. Although exponer is related to expose, here it means to present, especially in an academic or formal setting.

So pude exponer means:

• I was able to give my presentation
• I managed to present

In Spain, exponer is commonly used for presenting a topic in class, at work, or in a formal talk.

After sin, Spanish normally uses:

• a noun, or
• an infinitive

So sin ponerme nervioso literally means without getting nervous.

You cannot use a fully conjugated verb after sin in this structure.

Also, because ponerse is reflexive, the pronoun attaches to the infinitive:

• ponerme
• ponerte
• ponerse

Examples:

• Salió sin despedirse. = He left without saying goodbye.
• Lo hizo sin pensarlo. = He did it without thinking about it.

Yes, nervioso is an adjective, and the expression ponerse nervioso means to become nervous.

This is a very common Spanish pattern:

• ponerse + adjective = to become + adjective

Examples:

• ponerse triste = to become sad
• ponerse serio = to get serious
• ponerse nervioso = to get nervous

So sin ponerme nervioso means without becoming nervous or more naturally without getting nervous.

Because the adjective agrees with the speaker.

• A male speaker would say nervioso
• A female speaker would say nerviosa

So if the speaker is a woman, the sentence would be:

Después de haber preparado el esquema, me sentí tan segura que pude exponer sin ponerme nerviosa.

Notice that seguro would also change to segura.

In Spanish, object and reflexive pronouns can attach to:

• infinitives
• gerunds
• affirmative commands

Since poner is an infinitive here, the pronoun is attached:

• ponerme

This is the normal form after sin when using an infinitive.

Compare:

• No quiero ponerme nervioso.
• Estoy poniéndome nervioso.
• Ponte nervioso would be grammatical, but the meaning would be strange in most contexts.

The phrase Después de haber preparado el esquema is an introductory time expression. The comma helps separate that background information from the main clause:

• Después de haber preparado el esquema, = After having prepared the outline,
• me sentí tan seguro... = I felt so confident...

In Spanish, commas after introductory phrases are common and often help readability, especially when the phrase is fairly long.

Yes. The original sentence is perfectly correct, but in everyday speech some speakers might choose a slightly simpler version, such as:

• Después de preparar el esquema, me sentí tan seguro que pude exponer sin ponerme nervioso.
• Como había preparado el esquema, me sentí tan seguro que pude exponer sin ponerme nervioso.

The original version is still natural, especially in writing or in more careful speech. It just sounds a bit more explicit because of haber preparado.

Because the sentence refers to a specific completed event in the past.

• me sentí presents the feeling as a completed reaction at that moment
• pude presents the presentation as a completed success

If you used the imperfect, the meaning would be more about background, repeated situations, or an ongoing state:

• me sentía seguro = I felt confident / I was feeling confident
• podía exponer = I could present / I was able to present

But here the speaker is talking about one particular instance, so the preterite is the natural choice.