Nivelul de energie depinde de talie.

Because Romanian puts the definite article at the end of the noun.

• nivel = a level
• nivelul = the level

So nivelul de energie means the energy level.

This is very common in Romanian:

• băiat = a boy
• băiatul = the boy
• carte = a book
• cartea = the book

Romanian often uses de + noun where English uses a noun directly before another noun.

So:

• nivel de energie = literally level of energy
• natural English: energy level

This pattern is extremely common in Romanian:

• sticlă de apă = bottle of water
• sală de sport = gym
• nivel de stres = stress level

In this sentence, nivelul de energie is the normal way to say the energy level.

They do two different jobs.

1. In nivelul de energie, de links two nouns and means something like of.
2. In depinde de, de belongs to the verb phrase a depinde de, which means to depend on.

So the sentence has:

• nivelul de energie = the energy level
• depinde de talie = depends on size / waist / build, depending on context

Even though both words are de, they are not doing the same thing.

Yes. The verb is a depinde de = to depend on.

That means when you use this verb, you normally need de after it.

Examples:

• Depinde de vreme. = It depends on the weather.
• Totul depinde de tine. = Everything depends on you.
• Succesul depinde de muncă. = Success depends on work.

So depinde de talie is completely normal Romanian.

Talie can have several meanings depending on context. The most common one is waist, but it can also refer to build, stature, or size in some contexts.

So in a sentence like this, the exact English word depends on what meaning was intended in the wider context.

Common possibilities:

• waist
• body size
• build
• stature

If the translation you were shown says size, that is probably the sense intended here, not just waist in the narrow anatomical sense.

Because here it is being used in a general sense, not as a specific identified waist/size.

• depinde de talie = depends on size/build in general
• depinde de talia ei = depends on her waist / her size
• depinde de talia corpului = depends on the body's size/build

Romanian often uses a bare noun after a preposition when speaking generally.

You might hear it, and it is grammatically possible, but nivelul de energie is the more natural everyday way to say energy level.

There is a nuance:

• nivelul de energie = the standard expression for energy level
• nivelul energiei = more literally the level of the energy, which can sound more specific, more formal, or less idiomatic depending on context

So for a learner, nivelul de energie is the best version to remember.

Because the subject is singular: nivelul de energie.

The main noun in that subject is nivelul = the level, which is singular, so the verb must also be singular:

• Nivelul de energie depinde... = The energy level depends...

If the subject were plural, the verb would also be plural:

• Nivelurile de energie depind de talie. = Energy levels depend on size/build.

No. This is normal Romanian word order.

• Nivelul de energie = subject
• depinde = verb
• de talie = prepositional complement

So the structure is basically:

Subject + Verb + Complement

Romanian can change word order for emphasis, but this sentence is neutral and standard.

A helpful rough pronunciation is:

nee-VE-lul de eh-nehr-ZHEE-eh deh-PEEN-deh deh TAH-lee-eh

A slightly more accurate breakdown:

• nivelul → ni-VE-lul
• energie → e-ner-JI-e
• depinde → de-PIN-de
• talie → TA-li-e

A useful thing to notice is that energie and talie both have two clear vowels at the end:

• energie = ...ji-e
• talie = ...li-e

So they are not pronounced like one syllable at the end.