Eu nu merg fără cască când strada este aglomerată.

Yes. In Romanian, the verb ending already shows the subject, so merg by itself means I go.

• (Eu) merg = I go
• (Tu) mergi = you go

So eu is optional here. It may be included for:

• emphasis: I don’t go without a helmet...
• contrast: Eu nu merg..., dar el merge.
• clarity, especially for learners or in longer sentences

A more neutral version would simply be:

• Nu merg fără cască când strada este aglomerată.

Romanian usually makes a verb negative by putting nu directly before the verb.

• merg = I go
• nu merg = I do not go / I don’t go

Unlike English, Romanian does not need a helper like do.

So:

• I don’t go → nu merg
• not nu fac merge or anything similar

In this sentence, the pattern is:

• Eu + nu + merg + ...

A merge can mean several things depending on context:

• to go
• to walk
• to travel / move
• sometimes even to work / function for machines

In this sentence, merg most naturally means go in a general sense. Depending on the situation, an English speaker might interpret it as:

• I don’t go
• I don’t head out
• I don’t travel / move around

If you wanted to be more specific in Romanian, you might say:

• merg pe jos = I walk
• merg cu bicicleta = I go by bike / I ride a bike
• conduc = I drive

So merg here is broad and flexible.

After fără (without), Romanian often uses a noun without an article when speaking in a general sense.

• fără cască = without a helmet

This is the most natural way to express the general idea.

Compare:

• fără cască = without a helmet, helmetless in general
• fără o cască = without a helmet / without any helmet, more emphatic or less neutral
• fără casca = without the helmet, meaning a specific helmet

So in your sentence, fără cască is the normal generic form.

Cască is singular.

Useful forms are:

• o cască = a helmet
• casca = the helmet
• căști = helmets
• căștile = the helmets

In the sentence fără cască, the noun is singular and indefinite, used in a general way.

Because strada is the definite form:

• stradă = a street
• strada = the street

Romanian usually puts the definite article at the end of the noun, not before it as English does.

So:

• stradă → a street
• strada → the street

Here, strada este aglomerată means the street is crowded/busy.

Because adjectives in Romanian agree with the noun they describe.

Here the noun is:

• strada = the street

And stradă / strada is feminine singular, so the adjective must also be feminine singular:

• aglomerată

Compare:

• un drum aglomerat = a busy road
• o stradă aglomerată = a busy street

So the ending changes to match the noun.

It can mean both, depending on context.

In a sentence like this, with the present tense, it often has a habitual meaning:

• when / whenever the street is crowded

So the sentence can suggest a repeated behavior:

• Whenever the street is crowded, I don’t go without a helmet.

If the speaker means one specific occasion, context would make that clear.

Yes.

• este = is
• e = is

Both are correct. E is very common in everyday speech and informal writing.

So these are both fine:

• strada este aglomerată
• strada e aglomerată

The version with este sounds a bit more full or slightly more formal.

Yes. Romanian word order is fairly flexible.

Your sentence is:

• Eu nu merg fără cască când strada este aglomerată.

You could also say:

• Când strada este aglomerată, eu nu merg fără cască.
• Nu merg fără cască când strada este aglomerată.

These all mean essentially the same thing, though the emphasis changes slightly.

A useful punctuation note:

• If the când clause comes first, Romanian usually uses a comma:
  • Când strada este aglomerată, nu merg fără cască.

The Romanian ă is pronounced like a schwa sound, similar to the unstressed vowel in English sofa or about.

Examples:

• fără ≈ fuh-ruh
• cască ≈ KAS-kuh
• aglomerată ≈ a-glo-me-RA-tuh

It is a very common Romanian vowel, and it is different from:

• a as in casă
• â / î, which is a different central vowel

So in this sentence, noticing ă will help your pronunciation sound more natural.