Quanto mais cedo eu saio da garagem, menos tempo eu passo no trânsito.

This is a very common Portuguese pattern for expressing the idea of the more..., the less... or the earlier..., the less....

So:

• Quanto mais cedo... = The earlier...
• menos tempo... = the less time...

In other words, Portuguese uses quanto to build this comparative relationship:

• Quanto mais estudo, mais aprendo.
  The more I study, the more I learn.
• Quanto mais cedo eu saio, menos trânsito pego.
  The earlier I leave, the less traffic I hit.

Even though quanto often means how much in other contexts, here it is part of this fixed comparison structure.

Here, cedo means early, and it is functioning as an adverb, not an adjective.

• cedo = early
• mais cedo = earlier

So:

• Eu saio cedo. = I leave early.
• Eu saio mais cedo. = I leave earlier.

That is why Portuguese does not need a separate word for earlier here; it simply uses mais + cedo.

Portuguese often uses the present tense for:

• general truths
• habits
• repeated situations
• cause-and-effect statements

So this sentence is not necessarily about one specific day. It describes a general pattern:

• when I leave earlier, I spend less time in traffic

That is why eu saio and eu passo are in the present tense.

A more future-specific version could also exist, but this present-tense version sounds very natural for a general statement.

Saio is the 1st person singular form of sair (to leave / to go out).

Conjugation in the present:

• eu saio
• você/ele/ela sai
• nós saímos
• vocês/eles/elas saem

It is a little irregular because the eu form has an extra i:

• not eu sao
• but eu saio

This is just something you need to learn as part of the present tense of sair.

Because Portuguese normally contracts certain prepositions with articles.

Here:

• de + a garagem = da garagem

So:

• da garagem = from the garage

This kind of contraction is extremely common in Portuguese.

A few useful ones:

• de + o = do
• de + a = da
• em + o = no
• em + a = na

That also explains no trânsito in the sentence.

No is a contraction of:

• em + o = no

So:

• no trânsito literally means in the traffic

In natural English, this is usually translated as in traffic.

In Brazilian Portuguese, trânsito often refers to road traffic, traffic conditions, or the flow of cars in general.

So:

• passar no trânsito = to spend time in traffic
• ficar preso no trânsito = to be stuck in traffic

No. Portuguese often drops subject pronouns when the verb form already makes the subject clear.

So these are both natural:

• Quanto mais cedo eu saio da garagem, menos tempo eu passo no trânsito.
• Quanto mais cedo saio da garagem, menos tempo passo no trânsito.

Including eu can:

• add emphasis
• make the sentence feel a little clearer
• sound more conversational in some contexts

Brazilian Portuguese uses subject pronouns more often than European Portuguese, but they are still often optional.

Because tempo here means time as an uncountable idea, not separate countable units.

So Portuguese says:

• menos tempo = less time

Just like English says less time, not fewer times in this meaning.

Compare:

• Tenho menos tempo hoje. = I have less time today.

If you were talking about separate occasions, then a plural might make sense in a different sentence, but not here.

Yes, absolutely. That is very natural Portuguese.

Full version:

• Quanto mais cedo eu saio da garagem, menos tempo eu passo no trânsito.

Shorter version:

• Quanto mais cedo saio da garagem, menos tempo passo no trânsito.

Both are correct. The shorter version is often preferred because Portuguese can sound smoother when unnecessary subject pronouns are omitted.

Yes, but it changes the feel a little.

• Quanto mais cedo eu saio..., menos tempo eu passo...
  This sounds like a general rule or habitual pattern.

• Quanto mais cedo eu sair..., menos tempo eu vou passar...
  This sounds more like a specific future situation.

So if you are talking about your everyday commuting logic, the present tense is perfect. If you are talking about what will happen on a particular day, a future-oriented version may fit better.

Not always. Garagem can mean:

• a home garage
• a parking garage
• a parking space
• a place where a car is kept

In this sentence, it most likely means the place where the speaker’s car starts out, probably at home or in a building.

So sair da garagem is basically leave the garage / pull out of the garage.

Yes, the comma is standard and helpful here.

The sentence has two linked parts:

• Quanto mais cedo eu saio da garagem
• menos tempo eu passo no trânsito

The comma separates the two halves of the comparison, much like a pause in English:

• The earlier I leave the garage, the less time I spend in traffic.

You may sometimes see punctuation handled loosely in informal writing, but using the comma is the normal and recommended choice.

Literally, the verb is passar, which often means to pass, but in many contexts it also means to spend time.

So:

• passar no trânsito here means to spend time in traffic

This is similar to other uses of passar:

• Passei duas horas estudando.
  I spent two hours studying.
• Passei muito tempo esperando.
  I spent a lot of time waiting.

So you should not translate passo too literally here. In this sentence, spend is the natural meaning.