Eu preciso de natas para fazer o molho.

Yes. In Portuguese, subject pronouns are often omitted when the verb form already makes the subject clear.

So:

Eu preciso de natas para fazer o molho.
and
Preciso de natas para fazer o molho.

both mean the same thing.

Because preciso is the I form, a Portuguese speaker usually does not need to say Eu unless they want emphasis, contrast, or extra clarity.

Here, preciso is the 1st person singular present tense form of the verb precisar, which means to need.

Present tense:

• eu preciso = I need
• tu precisas = you need
• ele/ela precisa = he/she needs
• nós precisamos = we need
• vós precisais = you need
• eles/elas precisam = they need

So Eu preciso simply means I need.

Because precisar is very commonly used as precisar de + noun in Portuguese, especially in standard European Portuguese.

So:

• preciso de natas = I need cream
• precisas de ajuda = you need help
• precisamos de tempo = we need time

This is different from English, where need takes a direct object without a preposition.

A native English speaker may want to say something like preciso natas, but standard Portuguese needs de here: preciso de natas.

Yes. Preciso can also be an adjective meaning precise, accurate, or exact.

For example:

• um valor preciso = an exact value
• uma resposta precisa = a precise answer

But in your sentence, preciso is definitely a verb, not an adjective, because it is part of eu preciso de... = I need...

That is just how Portuguese normally expresses this idea. In Portugal, natas is the usual word for cream as a food ingredient, even though English uses a singular mass noun.

So you should learn it as a normal expression:

• natas = cream

The singular nata exists, but in everyday cooking language natas is the usual form when talking about cream as an ingredient.

Yes, this is one of the things that sounds very European Portuguese.

In Portugal, people usually say natas for dairy cream.
In Brazil, the usual term is creme de leite.

So:

• Portugal: preciso de natas
• Brazil: preciso de creme de leite

Both refer to the same general ingredient, but the vocabulary differs.

Para + infinitive is a very common way to express purpose in Portuguese.

So:

• para fazer o molho = to make the sauce / in order to make the sauce

Other examples:

• comprei pão para fazer sandes = I bought bread to make sandwiches
• preciso de dinheiro para viajar = I need money to travel

So in your sentence, para fazer o molho explains why the speaker needs the cream.

Portuguese often uses the definite article more than English does.

Here, o molho suggests a particular sauce, probably the one both speaker and listener already have in mind, such as the sauce for a recipe they are discussing.

So:

• fazer o molho = make the sauce
• fazer molho = make sauce / make a sauce

Both can exist, but o molho sounds more specific. It often feels natural in context when there is one expected sauce.

The tricky part is lh.

In European Portuguese, molho is pronounced approximately MO-lyu, with the lh sounding similar to the lli in some pronunciations of million, though it is not exactly the same.

A rough guide:

• molho ≈ MO-lyu

A few pronunciation notes:

• lh is a single consonant sound in Portuguese
• the final o in European Portuguese is usually reduced, often sounding like u

So the word does not sound like English mol-ho.

Yes, a little.

The original order is very natural:

• Eu preciso de natas para fazer o molho.

But you could also say:

• Preciso de natas para fazer o molho.
• Para fazer o molho, preciso de natas.

The second version puts the purpose first, so it gives slightly more emphasis to making the sauce.

What you normally should not do is break up fixed parts of the sentence in unnatural ways. The basic chunks are:

• preciso de natas
• para fazer o molho

Keeping those chunks together will help your Portuguese sound natural.