Después de lavarme el pelo, uso acondicionador para que la coleta no quede tan tirante.

After después de, Spanish normally uses either:

• a noun: después del trabajo
• or an infinitive: después de comer, después de lavarme el pelo

So después de lavarme el pelo means after washing my hair.

Me lavo is a fully conjugated verb, so it does not fit after después de by itself. If you wanted a full clause, you would need something like después de que me lave or después de que me lavé, depending on the meaning.

The -me is the reflexive pronoun for yo.

The verb is lavarse el pelo, literally to wash oneself the hair, which is how Spanish commonly expresses to wash one’s hair.

So:

• lavarme = to wash myself
• lavarte = to wash yourself
• lavarse = to wash himself/herself/yourself

With an infinitive, the reflexive pronoun is usually attached to the end:

• lavarme
• peinarme
• ducharme

Spanish often uses the definite article (el, la, los, las) instead of a possessive adjective when talking about body parts, clothing, and personal items, especially when the owner is already clear from the reflexive pronoun.

So:

• me lavo el pelo = I wash my hair
• me cepillo los dientes = I brush my teeth
• me pongo la chaqueta = I put on my jacket

Using mi pelo is possible, but here el pelo sounds more natural.

Because Spanish usually omits subject pronouns when the verb ending already shows who the subject is.

• uso clearly means I use
• usas = you use
• usa = he/she/you use

So yo uso acondicionador is grammatical, but uso acondicionador is more natural unless you want emphasis or contrast.

The present tense here describes a habit or routine.

So Después de lavarme el pelo, uso acondicionador means something like:

• After washing my hair, I use conditioner
• Whenever I wash my hair, I use conditioner

Spanish uses the present tense very often for regular actions like this.

Use para + infinitive when the subject stays the same:

• Uso acondicionador para desenredar el pelo
  = I use conditioner to detangle my hair

Use para que + verb when there is a new clause after it:

• Uso acondicionador para que la coleta no quede tan tirante
  = I use conditioner so that the ponytail doesn’t end up so tight

Even though the overall subject is still the same person, la coleta is now the grammatical subject of quede, so Spanish uses para que.

Because para que normally triggers the subjunctive.

So:

• queda = present indicative
• quede = present subjunctive

After expressions of purpose like para que, Spanish uses the subjunctive because the result is intended or desired, not simply stated as a fact.

That is why you get:

• para que la coleta no quede tan tirante

Here quedar means something like to end up, to turn out, or to look/feel after being arranged.

So que la coleta no quede tan tirante means:

• so that the ponytail doesn’t end up so tight
• so that the ponytail isn’t left so tight
• so that the ponytail doesn’t feel/look so tight

This is a very common use of quedar in Spanish when talking about how something turns out after doing it.

In Spain, coleta commonly means ponytail.

This is a good example of regional vocabulary. In other Spanish-speaking countries, other words may be more common, such as cola de caballo.

So if you are learning Spanish from Spain, coleta is a very natural word here.

Here tirante means tight, pulled tight, or tense from being pulled.

When talking about hairstyles, skin, or anything being stretched, tirante suggests a feeling of pulling.

So una coleta tirante is a tight ponytail, especially one that pulls on the scalp.

Both relate to degree, but they are used differently.

• muy tirante = very tight
• tan tirante = so tight

In this sentence, tan fits naturally because the idea is about preventing an excessive degree:

• para que la coleta no quede tan tirante
  = so that the ponytail doesn’t end up so tight

It implies not that tight or not as tight. Spanish often uses tan in this kind of negative result clause.

Because in Spanish, no goes directly before the conjugated verb.

So:

• no quede
• no quiero
• no tengo

That is the normal word order for negation in Spanish.

Yes. Pelo and cabello can both mean hair.

In many contexts:

• pelo is more everyday and common
• cabello can sound a bit more formal or stylistically careful

In Spain, lavarme el pelo sounds completely natural in daily speech. Lavarme el cabello is correct too, but a little less conversational.