Learn Hardcore Spanish (Spain): No debes ponerte celoso cuando tu pareja sale con sus amigas. - You must not get jealous when your partner goes out with her friends.

poner (non‑reflexive) = to put / to place something
- Pongo el libro en la mesa. – I put the book on the table.
ponerse (reflexive) = to put something on yourself, or to become a state
- Me pongo la chaqueta. – I put my jacket on.
- Me pongo nervioso. – I get nervous.

In ponerte celoso, te refers to tú and signals that you undergo the change of state: you get jealous.

Could I say No te debes poner celoso instead of No debes ponerte celoso?

Yes. Both are correct and natural:

No debes ponerte celoso.
No te debes poner celoso.

With constructions like deber + infinitive, the reflexive pronoun (me, te, se, nos, os) can go:

Attached to the infinitive: ponerte
Before the conjugated verb: te debes poner

Meaning and tone are the same; the version with the pronoun attached to the infinitive (ponerte) is slightly more common in speech.

Does No debes mean “you must not” or “you shouldn’t”?

Literally, deber is “to have to / must”, but in modern spoken Spanish:

No debes ponerte celoso is usually understood as “You shouldn’t get jealous”, not as a strict prohibition.

If you wanted a very strong must not, you’d typically add emphasis or use other forms:

No debes bajo ningún concepto ponerte celoso. – You must not, under any circumstances, get jealous.

For everyday advice, No debes ponerte celoso ≈ You shouldn’t get jealous.

Why is it celoso and not celosa? What if I’m talking to a woman?

The adjective celoso/celosa agrees with the person who gets jealous, i.e. with tú (the person being addressed).

Speaking to a man:
- No debes ponerte celoso.
Speaking to a woman:
- No debes ponerte celosa.

So in real use, you choose celoso or celosa depending on who tú is. The sentence you saw is the masculine version.

Why is pareja feminine if it can refer to a man?

In Spanish, nouns have grammatical gender, which isn’t always the same as the real‑world gender of the person.

la pareja is always grammatically feminine, regardless of whether your partner is male or female.

Examples:

Mi pareja es muy simpática. – My partner is very nice. (could be a man or a woman)
Su pareja es un chico italiano. – Their partner is an Italian guy.

So tu pareja is a gender‑neutral way to say “your partner” in Spanish (Spain), even though the word itself is grammatically feminine.

What exactly does salir con mean here? Could it also mean “to go out on a date”?

Yes, salir con can mean different things depending on context:

To go out / hang out with someone (socially)
- In this sentence: cuando tu pareja sale con sus amigas = when your partner goes out (socially) with her female friends.
To be going out with / to date someone
- Está saliendo con Marta. – He’s going out with Marta / dating Marta.

Here, because it’s “sale con sus amigas”, and amigas are clearly friends, the meaning is “goes out with her friends”, not “is dating them”.

Why is it cuando tu pareja sale (present indicative) and not cuando tu pareja salga (subjunctive)?

With cuando, Spanish uses:

Present indicative to talk about general, repeated, or habitual actions.
- No debes ponerte celoso cuando tu pareja sale con sus amigas.
  → whenever this happens, in general.
Present subjunctive (after a future reference) for future / hypothetical actions not seen as a routine:
- No debes ponerte celoso cuando tu pareja salga con sus amigas mañana.
  → when she goes out tomorrow (a specific future event).

Your sentence is a general rule/advice, so sale (indicative) is the natural choice.

Why is it sus amigas and not tus amigas? Whose friends are these?

Sus agrees with tu pareja, not with tú.

tu pareja = your partner (subject)
sus amigas = her/his/their friends (friends belonging to tu pareja)

If we said tus amigas, it would mean your (the listener’s) female friends, which would change the meaning to:

You shouldn’t get jealous when your partner goes out with your friends.

So sus here refers back to tu pareja.

Does sus mean “his”, “her”, or “their”? How do I know which one it is?

On its own, sus is ambiguous; it can mean:

his, her, its, their, or your (formal).

You find the meaning from context:

Here we have tu pareja (your partner) in singular, so sus amigas logically means “her friends” (or “his friends” if the partner is male).

If there were any doubt, Spanish often clarifies with de + pronoun/name:

las amigas de ella – her friends
las amigas de él – his friends

Why amigas and not amigos? What’s the difference?

Spanish marks grammatical gender in plural nouns:

amigos = group of all men or mixed men and women
amigas = group of all women

So sus amigas implies the partner is going out with female friends.
If the group is mixed or unknown, speakers normally default to amigos:

sale con sus amigos – goes out with his/her friends (mixed or unspecified).

Can I move the cuando clause to the beginning, like in English?

Yes, both word orders are correct:

No debes ponerte celoso cuando tu pareja sale con sus amigas.
Cuando tu pareja sale con sus amigas, no debes ponerte celoso.

If the cuando clause comes first, it’s common (though not obligatory) to put a comma:

Cuando tu pareja sale con sus amigas, no debes ponerte celoso.

Meaning and tone are the same.

How would this sentence change if I wanted to be more formal and use usted instead of tú?

You need to change:

The possessive tu → su
The reflexive pronoun te → se
The verb form debes → debe

Result:

No debe ponerse celoso/celosa cuando su pareja sale con sus amigas.

Again, celoso vs celosa depends on whether usted is a man or a woman.