Se não tiveres cuidado, vais entornar o café no teclado.

Because after se meaning if, Portuguese often uses the future subjunctive when talking about a possible future situation.

• Se não tens cuidado would sound wrong here.
• Se não tiveres cuidado = If you are not careful / If you don’t be careful

This is a very common pattern in Portuguese:

• Se fores = if you go
• Se puderes = if you can
• Se tiveres = if you have

So tiveres is the future subjunctive of ter.

Vais entornar is the ir + infinitive future, which is extremely common in everyday Portuguese. It works a lot like you’re going to spill in English.

So:

• vais entornar = you’re going to spill

A more formal or literary alternative would be:

• entornarás o café no teclado

But in normal speech, especially in conversation, vais entornar sounds much more natural.

It is not written because Portuguese often leaves subject pronouns out when the verb already makes the person clear.

Here, the verbs show that the sentence is talking to tu:

• tiveres
• vais

So the full idea is:

• Se tu não tiveres cuidado, tu vais entornar o café no teclado.

But native speakers normally omit tu unless they want emphasis or contrast.

Because of the verb forms.

• tiveres is the form used with tu
• vais is also the form used with tu

If it were você, the sentence would be:

• Se não tiver cuidado, vai entornar o café no teclado.

So the original sentence is clearly addressing someone as tu.

Entornar means to spill, especially by tipping something over or letting liquid fall where it should not.

It is close to derramar, but there is a slight difference in feel:

• entornar often suggests overturning or accidentally spilling from a container
• derramar is a broader word for spilling or pouring out

In this sentence, entornar o café sounds very natural for spill the coffee.

Portuguese often uses the definite article more than English does.

So:

• o café = the coffee

Even where English might simply say coffee, Portuguese often prefers the article when referring to a specific drink already present in the situation.

Here it suggests the coffee you are holding or drinking.

No is a contraction of:

• em + o = no

So:

• no teclado literally means in/on the keyboard, depending on context

With objects and surfaces, Portuguese often uses em where English uses on.

So:

• entornar o café no teclado = spill the coffee on the keyboard

You could, but it would not sound as natural here.

• no teclado is the most idiomatic choice for liquid ending up on the keyboard
• sobre o teclado means more literally over/on top of the keyboard and can sound more spatial or formal

For accidents like this, Portuguese usually prefers em/no.

Because in Portuguese, negation normally goes directly before the verb.

So:

• não tiveres = do not have / are not

This is the standard position:

• não sei = I don’t know
• não quero = I don’t want
• se não tiveres cuidado = if you are not careful

Yes, literally it is to have care, but in natural English it means:

• to be careful
• to take care

So:

• Se não tiveres cuidado = If you’re not careful

This is a very common expression in Portuguese:

• Tem cuidado! = Be careful!
• Tens de ter cuidado. = You have to be careful.

Yes. It is a very typical warning structure in Portuguese:

• Se + future subjunctive, then a consequence

So the sentence means something like:

• If you’re not careful, you’re going to spill the coffee on the keyboard.

It sounds natural, conversational, and slightly cautionary.

In European Portuguese, several vowels are reduced in normal speech, so it may sound more compact than it looks.

Roughly:

• Se não tiveres cuidado may sound a bit like s’ não tivéres cuidádu
• vais entornar o café no teclado may sound closer to vaiz entornár u café nu tecládu

A few things to notice:

• s in vais links to the next vowel and sounds like z: vaiz entornar
• unstressed o often sounds like u
• unstressed vowels are often weakened in European Portuguese

So the written form is straightforward, but the spoken form may feel more compressed to learners.

Word for word, yes, that is close to the structure:

• Se = if
• não tiveres = you do not have
• cuidado = care / caution
• vais entornar = you are going to spill
• o café = the coffee
• no teclado = on the keyboard

But natural English would be:

• If you’re not careful, you’re going to spill the coffee on the keyboard.

So the literal breakdown is useful for grammar, while the natural translation is better for real usage.