No quiero manchar la camisa blanca con salsa.

Because after querer (to want), Spanish normally uses an infinitive if the subject stays the same.

• quiero manchar = I want to stain
• quiero comer = I want to eat
• quiero salir = I want to leave

So No quiero manchar... means I don’t want to stain...

Mancho would be the conjugated form meaning I stain or I do stain, which does not fit after quiero.

In Spanish, no usually goes directly before the conjugated verb.

• No quiero = I don’t want
• No puedo = I can’t
• No entiendo = I don’t understand

So:

• No quiero manchar la camisa blanca con salsa.

is the normal way to say I don’t want to stain the white shirt with sauce.

Manchar means to stain, to mark, or to get something dirty with a spot or substance.

In this sentence, manchar is especially appropriate because sauce would leave a stain on the shirt.

Compare:

• manchar la camisa = to stain the shirt
• ensuciar la camisa = to dirty the shirt

Both can work in some situations, but manchar is more natural when you are talking about something like sauce, wine, ink, etc. leaving a visible mark.

Spanish often uses the definite article (el, la, los, las) more than English does.

So la camisa blanca literally means the white shirt, but depending on context it can still sound natural even if English might sometimes say my white shirt or just a white shirt.

In this sentence, la points to a specific shirt, probably one already known in the situation.

• la camisa blanca = the white shirt

If you wanted a white shirt, you would say:

• una camisa blanca

In Spanish, most adjectives usually come after the noun.

• camisa blanca = white shirt
• coche rojo = red car
• casa grande = big house

So camisa blanca is the normal word order.

Also, blanca changes form to match camisa, which is:

• feminine
• singular

That is why it is blanca, not blanco.

Because adjectives in Spanish must agree with the noun in gender and number.

• camisa is feminine singular
• so the adjective must also be feminine singular
• therefore: blanca

Examples:

• camisa blanca = feminine singular
• pantalón blanco = masculine singular
• camisas blancas = feminine plural
• pantalones blancos = masculine plural

It is the direct object of manchar.

The verb manchar is happening to the white shirt:

• manchar la camisa blanca = to stain the white shirt

You can test this by replacing it with a pronoun:

• No quiero mancharla. = I don’t want to stain it.

Here, la refers to la camisa blanca.

Here con salsa means with sauce, but more naturally in English we understand it as by getting sauce on it.

So con introduces the substance causing the stain.

• manchar la camisa con salsa = to stain the shirt with sauce
• manchar el mantel con vino = to stain the tablecloth with wine

So yes, con often means with, but here it tells you what substance causes the stain.

Yes, that is possible, and native speakers would understand it. But there is a slight nuance:

• manchar focuses on staining / leaving a mark
• ensuciar focuses more generally on making dirty

Because sauce usually leaves a visible stain, manchar is especially natural here.

If you are worried specifically about ruining the shirt with a stain, manchar is the better choice.

Yes, that is grammatically possible, but it is less neutral than:

• No quiero manchar la camisa blanca con salsa.

The original order is the most natural and straightforward:

1. verb
2. object
3. extra information

Putting con salsa before la camisa blanca can sound a bit more marked or stylistic, as if you are emphasizing the sauce.

So for a learner, the original sentence is the safest model.

Because that would create a different structure and would sound unnatural for this meaning.

• No quiero manchar... = I don’t want to stain...

That is the normal way to say it.

If you said quiero no manchar, that would literally mean something like I want not to stain, which is sometimes grammatically possible in Spanish but is less common and less natural in an everyday sentence like this.

So the standard choice is:

• No quiero manchar la camisa blanca con salsa.

Yes. Since manchar is an infinitive after quiero, the direct object pronoun can either go:

1. before the conjugated verb
2. attached to the infinitive

So both are correct:

• No la quiero manchar con salsa.
• No quiero mancharla con salsa.

The second one, No quiero mancharla con salsa, is especially common and natural.

In Spain, camisa usually means a shirt, especially a more traditional button-up style shirt. It is not normally the general word for any top.

For example:

• camisa = shirt
• camiseta = T-shirt

So if the clothing item is specifically a shirt, camisa is the right word here.