No pises el suelo mojado del balcón, que puedes resbalar.

Because this is a negative command addressed to tú.

In Spanish, negative commands use the present subjunctive:

• pisar → pises
• so: No pises = Don’t step on

Compare:

• Pisas = you step / you are stepping
• Pisa = he/she steps or a usted command
• No pises = don’t step when speaking informally to one person

So the sentence is using the standard tú negative imperative.

In Spanish, negative commands are formed with the present subjunctive, not the ordinary imperative form.

So:

• Positive command: Pisa con cuidado = Step carefully
• Negative command: No pises ahí = Don’t step there

This is a rule learners just have to get used to:
negative tú commands = no + present subjunctive.

Pisar literally means to step on, to tread on, or to set foot on something.

In this sentence:

• No pises el suelo mojado del balcón
  means Don’t step on the wet balcony floor

It is more specific than just to walk. The focus is on putting your foot onto a surface.

Yes, but there is an important regional difference.

In Spain, suelo is the most natural word for floor in this kind of sentence:

• el suelo del balcón = the balcony floor

In many parts of Latin America, piso can also mean floor. But in Spain, piso very often means flat/apartment, so suelo is clearer here.

So for Spanish from Spain, suelo is very natural.

Del is a contraction of de + el:

• de = of / from
• el balcón = the balcony
• del balcón = of the balcony

So:

• el suelo mojado del balcón = the wet floor of the balcony

In natural English, we would usually say the wet balcony floor, but Spanish often uses noun + de + noun.

Because in Spanish, adjectives often come after the noun.

So:

• el suelo mojado = the wet floor

This is the normal position for a descriptive adjective.
Putting the adjective before the noun is sometimes possible in Spanish, but it often changes the tone or emphasis. Here, suelo mojado is simply the normal, neutral order.

Here que introduces the reason or warning, and it sounds very natural in everyday Spanish.

So:

• No pises el suelo mojado del balcón, que puedes resbalar.

is like saying:

• Don’t step on the wet balcony floor, because you could slip.

This que is very common in spoken Spanish, especially for giving explanations, warnings, or justifications.

You could also say:

• ..., porque puedes resbalar

Both are correct, but que often sounds a bit more immediate and conversational in this kind of warning.

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

• resbalar = to slip
• resbalarse can also be used, often with a similar meaning

So you may hear:

• puedes resbalar
• te puedes resbalar

In this sentence, puedes resbalar is completely natural and means you could slip.

Spanish often allows both reflexive and non-reflexive versions with certain movement-related verbs, depending on style, region, and nuance. Here, the non-reflexive version is simple and idiomatic.

Puedes resbalar means you could slip or you might slip, so it expresses possibility/risk, not certainty.

That fits the warning well:

• No pises... = Don’t step...
• que puedes resbalar = because you could slip

If you said vas a resbalar, that would sound more like you are going to slip, which is much stronger and more certain.

So puedes is used because the speaker is warning about a danger, not predicting an inevitable result.

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

• pises already tells us it is tú
• puedes also already tells us it is tú

So:

• No pises... que puedes resbalar

is more natural than:

• Tú no pises... que tú puedes resbalar

Including tú is possible, but it would usually add emphasis, contrast, or emotion.

It is informal, because it uses the tú forms:

• No pises
• puedes

If you wanted to say it formally to usted, you would say:

• No pise el suelo mojado del balcón, que puede resbalar.

And if speaking to several people in Spain (vosotros):

• No piséis el suelo mojado del balcón, que podéis resbalar.

So the original sentence is clearly directed at one person informally.

Yes, if the context is already clear.

For example:

• No pises el suelo mojado, que puedes resbalar.

This still sounds natural and means Don’t step on the wet floor, you could slip.

But del balcón helps specify which wet floor is meant. It is useful if there are several places or if the speaker wants to be precise.

Yes, it helps show that the second part is an explanation or warning.

• No pises el suelo mojado del balcón, que puedes resbalar.

The comma separates:

1. the command
2. the reason for it

In speech, there would usually be a slight pause there. It makes the sentence easier to understand and reflects the natural rhythm of Spanish.