Because in Spanish, affirmative commands attach object pronouns to the end of the verb.
So:
This is very common:
With negative commands, the pronoun goes before the verb instead:
The accent is there to keep the stress in the right place after adding me.
Without the pronoun, avisa is stressed naturally as:
When you attach me, the word becomes longer:
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:
This is very common when pronouns are attached to commands.
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:
Using ser would suggest more of an inherent or general characteristic. For example:
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:
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:
If the noun changed, the adjective would change too:
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:
Not:
Spanish uses the subjunctive after si only in different kinds of hypothetical structures, for example:
But in your sentence, si + indicative is correct.
You change the command form of avisar.
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:
In this sentence, both readings are possible:
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.