Ανάβω πάντα το φλας πριν μπω στην άλλη λωρίδα.

Literally, ανάβω means I light or I turn on.

In this sentence, it is used in the everyday Greek sense of turning on a light or signal, so ανάβω το φλας means I turn on the indicator / blinker / turn signal.

You will see ανάβω with many things:

• ανάβω το φως = I turn on the light
• ανάβω τα φώτα = I turn on the lights
• ανάβω το φλας = I turn on the turn signal

Because Greek usually leaves out the subject pronoun when the verb ending already shows who the subject is.

Here, ανάβω ends in -ω, which tells you it means I turn on.
So εγώ is not necessary.

You could say Εγώ ανάβω πάντα το φλας... if you want emphasis, but normally Greek prefers the shorter version.

Πάντα means always. Its position is fairly flexible, but the placement here is very natural.

So:

• Ανάβω πάντα το φλας... = very natural
• Πάντα ανάβω το φλας... = also correct, with a bit more emphasis on always

Greek adverbs often move around more freely than in English, as long as the meaning stays clear.

Το φλας means the indicator / blinker / turn signal.

It is a very common everyday word in Greek, and it is a loanword. In driving contexts, Greeks often say φλας rather than a more formal term.

A few useful notes:

• it is treated as neuter
• that is why it takes το
• it usually does not change form much, since it is a borrowed word

So:

• το φλας = the turn signal
• ανάβω το φλας = I turn on the turn signal

Because Greek normally uses the singular here.

Even though a car has more than one signal light, the phrase ανάβω το φλας is the standard way to talk about signaling. It refers to the signaling action/device in a general practical way.

So Greek says:

• ανάβω το φλας not usually
• ανάβω τα φλας in this meaning

Μπω is the aorist subjunctive form of μπαίνω (I enter / I go in).

More specifically:

• dictionary form: μπαίνω
• aorist stem/form used here: μπω

In this sentence, it means before I enter / move into.

So:

• πριν μπω = before I enter / before I move into

Because after πριν (before), Greek normally uses a subjunctive form, and here the natural choice is the aorist subjunctive: μπω.

That is because the action is seen as:

• one complete event
• entering/moving into the lane

If you used μπαίνω, that would be the present-system form and would not sound natural here.

So:

• πριν μπω = before I enter / before I move into
  is the correct and idiomatic choice.

Because after πριν, Greek very often uses the subjunctive without να, especially in common everyday sentences like this one.

So:

• πριν μπω = very natural and standard

You may also hear:

• πριν να μπω

But πριν μπω is the more compact and very common version.

This part breaks down like this:

• στην = σε + την
• άλλη = other / another
• λωρίδα = lane

So στην άλλη λωρίδα literally means into/in the other lane.

A few grammar points:

• λωρίδα is feminine
• that is why you get την
• άλλη agrees with λωρίδα in gender, number, and case

So:

• η λωρίδα = the lane
• την άλλη λωρίδα = the other lane
• στην άλλη λωρίδα = into the other lane / in the other lane

It can suggest either the other lane or another lane, depending on context.

In a driving sentence like this, it usually means the other lane in the practical sense of the lane I’m moving into.

So English might translate it as:

• the other lane
• another lane
• the next lane over

But the Greek word άλλη itself basically means other / another, not specifically next.

Yes. It is natural Greek.

Literally, it means enter the other lane, but in driving context that is a normal way to express move into / change into the other lane.

Greek can also use other phrasing, for example:

• πριν αλλάξω λωρίδα = before I change lane
• πριν μπω στην άλλη λωρίδα = before I move into the other lane

Both are natural, but the sentence you were given is completely idiomatic.

Because Greek uses the definite article very often, often more than English does.

Here:

• το φλας = the turn signal
• στην άλλη λωρίδα = into the other lane

Even when English might sometimes sound fine without the, Greek often prefers the article in ordinary speech.

So using the articles here is completely normal and expected.