Después de la ducha, dejo el gel al lado del lavabo.

Después de means after. It is a fixed expression used before a noun.

• después = after / afterwards
• de = of
• la ducha = the shower

So Después de la ducha means After the shower.

Spanish often uses this structure:

• después de + noun
• después de comer = after eating
• después del trabajo = after work

In your sentence, it sets the time frame first: After the shower, ...

Dejo already includes the subject I. In Spanish, the verb ending often tells you who is doing the action, so subject pronouns are often omitted.

• dejo = I leave
• dejas = you leave
• deja = he/she leaves
• dejamos = we leave

So:

• Yo dejo el gel... = correct, but usually unnecessary
• Dejo el gel... = more natural in many contexts

Spanish drops subject pronouns much more often than English does.

Dejo is the present simple form of dejar for yo.

Here it can mean:

• a habitual action: I leave the shower gel next to the sink
• something you normally do: After the shower, I leave the gel next to the sink

This is very common in Spanish. The present tense is often used for routines and habits.

Here dejar means to leave in the sense of to put/leave something somewhere.

So dejo el gel al lado del lavabo means:

• I leave the gel next to the sink
• or more naturally in some contexts, I put the gel next to the sink

Spanish dejar is often used when you place something somewhere and leave it there.

Examples:

• Dejo las llaves en la mesa. = I leave the keys on the table.
• Deja el móvil aquí. = Leave the phone here.

Spanish uses articles (el, la, los, las) more often than English. When talking about a specific thing, Spanish usually includes the article.

So:

• el gel = the gel

Even when English might say I leave shower gel next to the sink, Spanish normally says dejo el gel...

The article sounds natural because the speaker is referring to the specific gel being used.

Gel is a masculine noun in Spanish, so it takes el:

• el gel

There is not always a logical reason from meaning alone; grammatical gender has to be learned with the noun. A noun ending in a consonant can be masculine or feminine, so you usually need to memorize it with its article.

Useful habit:

• learn nouns as el gel, la ducha, el lavabo, not just gel, ducha, lavabo

Al lado de is a fixed expression meaning next to or beside.

It is made of:

• a
• el
• lado
• de

But because a + el = al, it becomes:

• al lado de = next to

Examples:

• al lado de la cama = next to the bed
• al lado del lavabo = next to the sink

You should learn al lado de as a whole expression.

Because in Spanish, de + el contracts to del.

So:

• de + el lavabo → del lavabo

This contraction is required in normal Spanish.

The two main contractions you need to know are:

• a + el = al
• de + el = del

That is why the sentence has:

• al lado del lavabo

not:

• a el lado de el lavabo

In this sentence, lavabo means sink or washbasin, especially the bathroom sink.

In Spain:

• lavabo usually refers to the bathroom basin/sink
• fregadero usually refers to the kitchen sink

So in this sentence, lavabo fits well because it is talking about after the shower, so the bathroom is the natural setting.

Because Spanish nouns have grammatical gender:

• la ducha = feminine
• el lavabo = masculine

The article has to agree with the noun:

• feminine singular → la
• masculine singular → el

There is no special rule here that explains both words together; they simply have different genders and must be learned that way.

Yes. Después de ducharme means after showering or after I shower.

Compare:

• Después de la ducha = after the shower
• Después de ducharme = after showering / after I shower

Both are natural, but they are slightly different in structure:

• después de + noun → después de la ducha
• después de + infinitive → después de ducharme

Both work well in Spanish.

The comma is natural and helpful here because Después de la ducha is an introductory time phrase.

• Después de la ducha, dejo el gel al lado del lavabo.

Without the comma, the sentence is still understandable:

• Después de la ducha dejo el gel al lado del lavabo.

But with the comma, the sentence is easier to read and more clearly divided.

Yes, Spanish word order is flexible.

The original sentence:

• Después de la ducha, dejo el gel al lado del lavabo.

Possible variations:

• Dejo el gel al lado del lavabo después de la ducha.
• El gel lo dejo al lado del lavabo después de la ducha.

The original version is very natural because it starts with the time expression, then gives the action.

Word order can change for emphasis, but the original is a clear, neutral option.

Yes, in context it very likely refers to shower gel.

Spanish often relies on context instead of always saying the full expression. So:

• el gel can mean the gel
• in a bathroom context, especially after a shower, it will often be understood as shower gel

If you wanted to be more specific, you could say:

• el gel de ducha = shower gel

But el gel is very natural if the context is clear.

Because article usage works differently in Spanish. Spanish often sounds more natural with a definite article where English might use no article at all.

In your sentence:

• la ducha
• el gel
• el lavabo

English might say:

• After showering, I leave shower gel next to the sink

But Spanish usually prefers the nouns with articles in this kind of sentence.

This is a common difference between the two languages, so it is worth getting used to it rather than translating word for word.