Cursul de prim ajutor începe azi.

Because cursul means the course, while curs just means course.

In Romanian, the definite article is usually attached to the end of the noun:

• curs = course
• cursul = the course

This is very different from English, where the is a separate word.

Literally, de prim ajutor means something like of first aid.

In this sentence, it describes what kind of course it is:

• cursul = the course
• de prim ajutor = of first aid / first-aid

So cursul de prim ajutor means the first aid course.

Romanian often uses de in this kind of structure, where English might use a noun directly as an adjective.

Because prim ajutor is a fixed expression meaning first aid.

Here, prim means first, but it is not being used as the first one in a counting sense. So Romanian uses:

• prim ajutor = first aid

not

• primul ajutor = the first aid

The version with -ul would sound unnatural here. Think of prim ajutor as a set phrase you just learn as a whole.

Because in the expression de prim ajutor, the noun is part of a descriptive phrase, not something being made definite by itself.

So Romanian says:

• un curs de prim ajutor = a first aid course
• cursul de prim ajutor = the first aid course

The definiteness is carried by cursul, the main noun. The phrase de prim ajutor just tells us what kind of course it is.

Începe is the 3rd person singular present tense of the verb a începe, which means to begin / to start.

So:

• eu încep = I begin
• tu începi = you begin
• el/ea începe = he/she/it begins

In this sentence, the subject is cursul, which is singular, so Romanian uses începe.

Romanian often leaves out subject pronouns when they are not needed.

English usually says:

• It begins today

But Romanian can simply say:

• Începe azi

or, with the subject included:

• Cursul de prim ajutor începe azi

Because the verb ending already helps show the person and number, Romanian does not need a separate it.

Yes. Both mean today.

• azi = today
• astăzi = today

Azi is a little shorter and often feels a bit more natural in everyday speech. Astăzi can sound slightly more formal or more careful, but both are completely normal.

So you could also say:

• Cursul de prim ajutor începe astăzi.

Yes. Romanian word order is fairly flexible.

The sentence:

• Cursul de prim ajutor începe azi.

is the most neutral way to say it.

But you could also say:

• Azi începe cursul de prim ajutor.

This puts more focus on azi.

Both are correct. Romanian often changes word order for emphasis or style more easily than English does.

A rough pronunciation guide:

• începe ≈ uhn-CHE-pe
• azi ≈ AHZ-ee

A few useful notes:

• î is a Romanian vowel that does not exist in English. It is a close central sound, somewhat like a tight, muted uh.
• ce in începe sounds like che in check.
• z in azi is a real z sound, not an s.

You do not need perfect pronunciation right away, but it helps to notice that Romanian spelling is usually quite regular.

Yes, but the meaning changes slightly.

• curs de prim ajutor = a first aid course / first aid course
• cursul de prim ajutor = the first aid course

So if you are speaking generally, you might use curs de prim ajutor. If you are talking about a specific course that both speaker and listener know about, cursul de prim ajutor is the right form.

Because de is the normal preposition for this kind of noun description in Romanian.

• curs de prim ajutor = first aid course
• manual de istorie = history textbook
• sală de sport = gym / sports hall

Using pentru would change the meaning. Pentru usually means for, often with a clearer idea of purpose or intended recipient. Here, Romanian is simply naming the type of course, so de is the natural choice.