Eu ghicesc combinația.

That is true. Romanian often leaves out the subject pronoun because the verb ending already shows who the subject is.

So:

• Ghicesc combinația = I guess the combination
• Eu ghicesc combinația = still I guess the combination, but with extra emphasis on I

Using eu can sound contrastive or emphatic, as in:

• Eu ghicesc combinația, nu el = I’m guessing the combination, not him

So in this sentence, eu is not required, but it is perfectly correct.

Ghicesc is the 1st person singular present tense form of the verb a ghici.

So:

• a ghici = to guess
• ghicesc = I guess

This is the form used with eu.

A few present-tense forms are:

• eu ghicesc = I guess
• tu ghicești = you guess
• el/ea ghicește = he/she guesses
• noi ghicim = we guess
• voi ghiciți = you all guess
• ei/ele ghicesc = they guess

In Romanian, g before e or i normally has a soft sound, like the j sound in English job.

To keep a hard g sound before e or i, Romanian uses gh.

So:

• ge / gi = soft sound
• ghe / ghi = hard g sound

That is why the verb is written ghici and ghicesc.

A good approximation is ghee-CHESK.

More exactly:

• ghi sounds like ghee
• ce sounds like che in check, but shorter
• sc at the end sounds like sk

The stress is on the second syllable:

• ghi-cesc

So: ghi-CHESC

Because combinația is the definite form.

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

So:

• combinație = a combination
• combinația = the combination

That means the sentence refers to a specific combination, not just any combination.

Ț is pronounced ts, like the end of English cats.

So combinația is roughly pronounced:

com-bi-NA-tsi-a

A few useful points:

• ț = ts
• -ia at the end is pronounced clearly
• the stress is on na

So it is not an English-style soft sh or zh sound.

It is the direct object, so it is in the accusative.

In this sentence:

• Eu = subject
• ghicesc = verb
• combinația = direct object

For many Romanian nouns, especially inanimate ones like this one, the accusative form looks the same as the nominative form. So there is no special extra ending here beyond the normal definite article.

Because pe is not normally used with inanimate direct objects like combinația.

Romanian often uses pe before specific human or animate direct objects, especially people.

For example:

• Văd fata / O văd pe fată can involve that marker with a person

But with an inanimate thing like the combination, you simply say:

• ghicesc combinația

So no pe is needed here.

Yes, Ghicesc combinația is completely natural and is probably the more neutral version in many contexts.

Romanian word order is fairly flexible. The version with eu puts more attention on the subject.

Compare:

• Ghicesc combinația. = neutral, everyday I guess/am guessing the combination
• Eu ghicesc combinația. = more emphatic, I guess/am guessing the combination

So both are correct, but they do not sound exactly the same in emphasis.

It can mean either, depending on context.

Romanian uses the present tense for both a simple present and an ongoing present in many situations.

So Eu ghicesc combinația could mean:

• I guess the combination
• I am guessing the combination

Context tells you which one is meant.

Not always. A ghici can mean:

• to guess
• to figure out
• to predict
• to intuit

The exact nuance depends on context.

With combinația, it often suggests trying to work out or correctly guess a code, password, or combination, not necessarily just making a wild random guess.