Avísame si el suelo está resbaladizo.

Because in Spanish, affirmative commands attach object pronouns to the end of the verb.

• avisa = let/notify
• me = me

So:

• avisa + me → avísame

This is very common:

• dime = tell me
• llámame = call me
• escúchame = listen to me

With negative commands, the pronoun goes before the verb instead:

• No me avises = don’t let me know / don’t warn me

Avisa is the informal singular command form, used with tú.

It comes from the verb avisar = to let know / to inform / to warn.

So avísame is speaking to one person you would address as tú.

Related forms:

• tú: avísame
• usted: avíseme
• vosotros (Spain, informal plural): avisadme
• ustedes: avísenme

The accent is there to keep the stress in the right place after adding me.

Without the pronoun, avisa is stressed naturally as:

• a-VI-sa

When you attach me, the word becomes longer:

• a-vi-sa-me

If you wrote avisame without an accent, Spanish spelling rules would make the stress fall on sa. The written accent keeps the original stress on vi:

• a-VI-sa-me → avísame

This is very common when pronouns are attached to commands.

Because si without an accent means if.

• si = if
• sí = yes

So here:

• Avísame si el suelo está resbaladizo = Let me know if the floor is slippery

If you wrote sí, it would mean yes, which would not fit this sentence.

Because estar is normally used for a state or condition, and being slippery is usually treated as a condition of the floor at that moment.

So:

• está resbaladizo = it is slippery right now / in this situation

Using ser would suggest more of an inherent or general characteristic. For example:

• Este material es resbaladizo = This material is slippery by nature

In your sentence, the idea is that the floor may currently be slippery, so está is the natural choice.

Here suelo means the floor or the ground surface.

In Spain, suelo is the most natural word for the physical surface you walk on indoors or outdoors.

About piso:

• In Spain, piso very often means apartment / flat
• It can also mean floor/storey of a building
• In some varieties of Spanish, it can also mean floor surface, but in Spain suelo is clearer here

So for Spain Spanish, el suelo está resbaladizo sounds very natural.

Because resbaladizo is an adjective meaning slippery or likely to cause slipping.

It agrees with suelo, which is masculine singular, so the adjective must also be masculine singular:

• el suelo resbaladizo

If the noun changed, the adjective would change too:

• la acera está resbaladiza = the pavement/sidewalk is slippery
• las escaleras están resbaladizas = the stairs are slippery
• los suelos están resbaladizos = the floors are slippery

No. Here you use the indicative: si el suelo está...

That is because this is a normal, real condition: if the floor is slippery.

So:

• Avísame si el suelo está resbaladizo ✅

Not:

• Avísame si el suelo esté resbaladizo ❌

Spanish uses the subjunctive after si only in different kinds of hypothetical structures, for example:

• Si estuviera resbaladizo, te avisaría = If it were slippery, I would let you know

But in your sentence, si + indicative is correct.

Yes. Both word orders are correct:

• Avísame si el suelo está resbaladizo
• Si el suelo está resbaladizo, avísame

The meaning is basically the same.

The difference is mainly one of focus:

• Avísame si... starts with the command, like English Let me know if...
• Si el suelo está..., avísame starts with the condition and highlights it first

Both are natural.

You change the command form of avisar.

• Informal singular (tú): Avísame si el suelo está resbaladizo.
• Formal singular (usted): Avíseme si el suelo está resbaladizo.
• Informal plural in Spain (vosotros): Avisadme si el suelo está resbaladizo.
• Plural/formal (ustedes): Avísenme si el suelo está resbaladizo.

So the rest of the sentence stays the same; only the command changes.

It can mean either, depending on context.

The verb avisar often covers ideas like:

• let someone know
• inform someone
• warn someone

In this sentence, both readings are possible:

• let me know if the floor is slippery
• warn me if the floor is slippery

If the context is safety, English might naturally translate it as warn me. If it is simply about passing on information, let me know fits well.