Se il GPS non funziona, rischio di sbagliare strada.

In Italian, it is very common to use the definite article with nouns, even when English would often leave it out.

So Italians normally say:

• il GPS
• il telefono
• la macchina

Here, GPS is treated as a masculine singular noun, so it takes il.

Italian often leaves out subject pronouns because the verb ending already shows who is doing the action.

• rischio = I risk
• rischi = you risk
• rischia = he/she risks

So rischio already tells you the subject is I, and io is unnecessary unless you want emphasis.

Here it is a verb: the 1st person singular present of rischiare.

• rischio = I risk

It can also be a noun in other contexts:

• Il rischio è alto = The risk is high

But in this sentence, because it is followed by di sbagliare, it is clearly the verb.

After rischiare, Italian usually uses di + infinitive when you mean to risk doing something.

So:

• rischio di sbagliare = I risk making a mistake / I might make a mistake
• rischi di arrivare tardi = you risk arriving late

This is a very common pattern:

• verb + di + infinitive

Funzionare means to work, to function, or to operate properly.

So il GPS non funziona means the GPS is not working correctly.

It is a very common verb for machines, devices, systems, apps, and even methods:

• Il computer non funziona
• Questa app non funziona
• Il piano funziona

Sbagliare strada is a very common expression meaning to take the wrong road, to go the wrong way, or more generally to head in the wrong direction.

The noun strada is used here in a fairly general, idiomatic way, so Italian often leaves out the article.

A native speaker is likely to say:

• Ho sbagliato strada
• Rischio di sbagliare strada

Using la is possible in some contexts, especially if you mean a more specific road, but the article-less version is the most natural in this kind of sentence.

This sentence expresses a real or likely condition:

• Se il GPS non funziona, rischio di sbagliare strada.

Italian commonly uses present + present for situations like this:

• If the GPS doesn’t work, I risk going the wrong way.

This is not a hypothetical would situation. It is more like a general real possibility.

Compare:

• Se ho tempo, ti chiamo. = If I have time, I call / I’ll call you.
• Se piove, restiamo a casa. = If it rains, we stay home.

Yes. Non va is very common and natural in everyday speech.

• Il GPS non va = The GPS isn’t working
• Il GPS non funziona = The GPS doesn’t work / isn’t functioning

The difference is mainly one of style:

• non va = more colloquial
• non funziona = a bit more explicit or neutral

Both are correct.

In Italian, people usually pronounce the letters separately:

• gi
  • pi
    • esse

So it sounds roughly like jee pee ESS-eh.

It is not usually pronounced like an Italian word, but as the three letter names.

It is standard and natural to use a comma when the se clause comes first:

• Se il GPS non funziona, rischio di sbagliare strada.

The comma helps separate the condition from the main clause. In very informal writing people may sometimes omit it, but using it here is the normal choice.