אני רוצה להכין לכם קפה.

A word-by-word breakdown is:

• אני = I
• רוצה = want
• להכין = to prepare / to make
• לכם = for you / to you (addressing more than one person, usually males or a mixed group)
• קפה = coffee

So the literal structure is basically I want to prepare for-you coffee.

Because Hebrew, like English, uses want + infinitive.

• רוצה = want
• להכין = to prepare

So רוצה להכין works like want to make.

This is a very common pattern in Hebrew:

• אני רוצה לאכול = I want to eat
• אני רוצה ללכת = I want to go
• אני רוצה להכין = I want to prepare

In normal unpointed writing, רוצה can represent both a male speaker and a female speaker.

But in pronunciation there is a difference:

• male speaker: rotze
• female speaker: rotza

So a man and a woman can both write אני רוצה להכין לכם קפה, but they would pronounce רוצה differently.

This happens because Hebrew present-tense forms agree with gender.

לכם means to you or for you.

It is made from:

• ל־ = to / for
• כם = you (plural masculine or mixed-gender group)

In this sentence, the most natural English meaning is for you:

• להכין לכם קפה = to make coffee for you

Hebrew often uses ל־ where English uses either to or for, depending on the context.

לכם is used when speaking to:

• more than one male
• or a mixed group

Other forms would be:

• לך = to/for you (one male)
• לך = to/for you (one female)
  In writing these look the same, but they are pronounced differently.
• לכן = to/for you (a group of females)

So:

• אני רוצה להכין לך קפה = I want to make you coffee (to one person)
• אני רוצה להכין לכן קפה = I want to make you coffee (to a group of women)

Sometimes Hebrew can drop subject pronouns, but in the present tense it usually keeps them more often than in the past or future.

That is because רוצה by itself does not clearly show person the way many past/future forms do. It mainly shows gender and number, not I / you / he clearly enough in all contexts.

So אני רוצה is the normal, clear way to say I want.

If you said only רוצה להכין לכם קפה, people might still understand from context, but it sounds less complete unless the subject is already obvious.

Because את is used before a definite direct object.

Here, קפה is indefinite: it means coffee or some coffee, not the coffee.

So:

• אני רוצה להכין לכם קפה = I want to make you coffee
• אני רוצה להכין לכם את הקפה = I want to prepare the coffee for you

Use את when the object is specific and definite.

Yes, that is basically the idea.

Hebrew often uses a bare noun where English might say:

• coffee
• some coffee
• a coffee
  depending on context

So קפה here is indefinite and general.

If you say הקפה, that means the coffee, a specific coffee already known in the conversation.

Yes. להכין קפה is very natural and common. It means to prepare coffee or to make coffee.

Another expression you may also hear is:

• לעשות קפה = to make coffee

But להכין קפה sounds very standard and natural in this sentence.

A common pronunciation guide is:

ani rotze / rotza le-hakhin lakhem kafe

A few notes:

• rotze = if the speaker is male
• rotza = if the speaker is female
• the kh sound in le-hakhin and lakhem is the throaty Hebrew sound, like the ch in Scottish loch or German Bach
• kafe is usually stressed on the last syllable: ka-FE

It can be natural, but it is slightly more literal as I want to make you coffee.

Depending on context, Hebrew speakers might also say:

• אני אכין לכם קפה = I’ll make you coffee
• אפשר להכין לכם קפה? = Can I make you coffee?
• רוצים קפה? = Do you want coffee?

So your sentence is correct and natural, but it expresses the speaker’s wish or intention more than a direct offer.