Sunt sigur de rezultat.

Romanian often leaves subject pronouns out because the verb form already shows the person.

• sunt = I am
• so Sunt sigur de rezultat already clearly means I am sure of the result

You can add eu for emphasis or contrast:

• Eu sunt sigur de rezultat, dar el nu este.
  I am sure of the result, but he isn’t.

Sunt is the present-tense form of a fi (to be). In this sentence it means am.

So:

• sunt = am
• sigur = sure
• de rezultat = of/about the result

Sigur is an adjective, and in Romanian adjectives agree with the person’s gender and number.

Here:

• sigur = masculine singular
• sigură = feminine singular

So:

• a male speaker: Sunt sigur de rezultat.
• a female speaker: Sunt sigură de rezultat.

Plural forms are:

• siguri = masculine or mixed plural
• sigure = feminine plural

Because Romanian normally uses the pattern sigur de + noun/pronoun.

So:

• sunt sigur de rezultat = I am sure of the result
• sunt sigur de asta = I am sure of that

This is just the standard Romanian construction. English uses sure of or sure about, but Romanian usually uses de here.

Yes, but only if what follows is a whole clause, not just a noun.

Compare:

• Sunt sigur de rezultat.
  I am sure of the result.

• Sunt sigur că rezultatul va fi bun.
  I am sure that the result will be good.

So:

• de
  • noun/pronoun
• că
  • full sentence/clause

Rezultat is the basic noun form, while rezultatul means the result with the definite article attached.

In Romanian, a bare noun after a preposition can sound more general or more neutral, especially in short expressions like this. If you want to make the noun clearly specific, you will often add more context, for example:

• Sunt sigur de rezultatul examenului.
  I am sure of the exam result.

• Sunt sigur de acest rezultat.
  I am sure of this result.

So rezultat in your sentence is not strange, but rezultatul is used when the definiteness is made more explicit.

Yes. Sunt can mean both I am and they are.

Context tells you which one it is. In this sentence, sigur is singular, so it matches I am.

Compare:

• Sunt sigur de rezultat.
  I am sure of the result.

• Sunt siguri de rezultat.
  They are sure of the result.

The adjective helps you tell the difference.

The normal, neutral order is:

• Sunt sigur de rezultat.

You can change the order for emphasis, but it becomes more marked:

• De rezultat sunt sigur.
  As for the result, I’m sure.

That sounds more contrastive or stylistic. For everyday use, the original order is best.

Not in this meaning. After sigur, Romanian normally uses de, not despre.

• correct: Sunt sigur de rezultat.
• unnatural/wrong here: Sunt sigur despre rezultat.

Despre usually means about/regarding, but it does not fit this common pattern.

Yes, it is understandable and natural enough, especially as a short example sentence.

In real conversation, Romanians might also say things like:

• Sunt sigur de asta.
  I’m sure of that.

• Sunt sigur că va fi bine.
  I’m sure it will be fine.

• Sunt sigur de rezultatul final.
  I’m sure of the final result.

So your sentence follows a normal Romanian structure, even if in real speech people often add a little more context.