Tengo da parte una fetta di torta per te.

As a whole, tenere da parte means to keep aside, to save, or to reserve.

In this sentence, it means that the speaker is keeping a slice of cake for someone so it does not get eaten by someone else.

So this is not just about physically holding something. It is an idiomatic expression, and in context it means something like:

• to keep aside for someone
• to save for someone
• to reserve for someone

Tengo is the first-person singular present indicative of tenere.

So:

• tengo = I keep / I am keeping
• infinitive: tenere = to keep, to hold

It is an irregular verb, so it is worth memorizing:

• tengo
• tieni
• tiene
• teniamo
• tenete
• tengono

No. Here tengo means I keep or I am keeping, not I have.

That matters because learners who know a little Spanish may expect tengo to mean I have, but in standard Italian that is not what is happening in this sentence.

In standard Italian:

• ho = I have
• tengo = I keep / I hold

There are regional varieties of Italian where tenere can sometimes be used more like avere, but in tenere da parte this is a normal standard expression meaning keep aside.

Da parte is a fixed expression that means aside, separately, or set aside.

So:

• tenere da parte = to keep aside
• mettere da parte = to put aside
• lasciare da parte = to leave aside

It is best not to translate da parte too literally word by word. In this sentence, it adds the idea that the slice is being kept separate for the person.

Because Italian normally drops subject pronouns when they are not needed.

The ending -o in tengo already tells you the subject is I.

So:

• Tengo da parte una fetta di torta per te = normal
• Io tengo da parte una fetta di torta per te = possible, but more emphatic

You would add io only if you want contrast or emphasis, for example:

• Io tengo da parte una fetta per te, lui no.
  I’m keeping a slice for you, he isn’t.

Yes, you could say un pezzo di torta, but una fetta di torta is more specific.

• fetta = slice
• pezzo = piece

For cake, fetta is very natural because cake is often served in slices.
Pezzo is more general and less precise.

So:

• una fetta di torta = a slice of cake
• un pezzo di torta = a piece of cake

Both are correct, but fetta is often the more idiomatic choice here.

After words like fetta, Italian often uses di + noun to say what something is a slice, piece, glass, or cup of.

So:

• una fetta di torta = a slice of cake
• un bicchiere d’acqua = a glass of water
• un pezzo di pane = a piece of bread

If you say una fetta della torta, that usually means a slice of the cake, referring to a specific cake already known in the conversation.

So the difference is roughly:

• una fetta di torta = a slice of cake, more general
• una fetta della torta = a slice of the cake, more specific

Because per te means for you, which is the idea here: the slice is intended for you.

• per te = for you
• a te = to you

In this sentence, the speaker is not focusing on giving the cake to you right now, but on keeping it for you.

A very common alternative is:

• Ti tengo da parte una fetta di torta.

Here ti expresses the person for whom the slice is being kept. This is often more natural in everyday Italian than using per te.

So both of these are good:

• Tengo da parte una fetta di torta per te.
• Ti tengo da parte una fetta di torta.

Yes. Italian word order is more flexible than English, although some versions sound more neutral than others.

The original sentence is fine:

• Tengo da parte una fetta di torta per te.

A very common alternative is:

• Ti tengo da parte una fetta di torta.

You can also move things for emphasis:

• Una fetta di torta te la tengo da parte.
  This emphasizes the slice of cake.

• Per te tengo da parte una fetta di torta.
  This emphasizes for you, though it is less neutral.

So the word order can change, but not every version sounds equally natural in every situation.

The present tense in Italian often covers both:

• a simple present idea: I keep
• an ongoing current situation: I’m keeping

In this sentence, the present describes the current state: the speaker has a slice set aside right now.

So tengo can feel like:

• I’m keeping a slice of cake for you
• I have a slice of cake saved for you

If you want to focus more on the action of setting it aside earlier, you could say:

• Ho messo da parte una fetta di torta per te.
  I set aside a slice of cake for you.

That version emphasizes the earlier action more clearly.

Yes, it is natural and standard Italian.

That said, many speakers would very naturally say:

• Ti tengo da parte una fetta di torta.

This sounds a little more direct and conversational.

Another common option is:

• Ti ho messo da parte una fetta di torta.

That one suggests the speaker has already set it aside.

So the original sentence is good, but depending on the situation, these are also very common:

• Ti tengo da parte una fetta di torta.
• Ti ho messo da parte una fetta di torta.