Se la misura non va bene, posso fare un reso entro domani.

Se means if and introduces a condition.

So the structure is:

• Se ... = If ...
• ..., posso ... = ..., I can ...

This is a very common Italian pattern for real, possible situations:

• Se piove, resto a casa. = If it rains, I stay home.
• Se la misura non va bene, posso fare un reso. = If the size isn’t right, I can make a return.

Here la misura means the size.

Literally, misura can also mean measurement, so learners often wonder about that. In shopping or clothing contexts, it can refer to the size or fit of an item.

That said, for clothes, la taglia is often even more common:

• Se la taglia non va bene... = If the size doesn’t fit / isn’t right...

So misura is understandable, but taglia may sound more specifically clothing-related.

Italian normally uses the definite article more often than English does.

So la misura is perfectly natural because it refers to the specific size of the item being discussed. Italian likes to make that relationship explicit with the article.

Compare:

• la misura
• la taglia
• il colore
• il prezzo

Even where English might be a little looser, Italian usually keeps the article.

Andare bene is a very common Italian expression meaning:

• to be okay
• to work
• to be suitable
• to fit, depending on context

So la misura non va bene literally looks like the size doesn’t go well, but naturally it means:

• the size isn’t right
• the size doesn’t work
• it doesn’t fit properly

This use of andare is extremely common in Italian:

• Va bene così. = That’s fine like that.
• Domani va bene? = Is tomorrow okay?
• Questa taglia non va bene. = This size isn’t right.

Usually, no.

In this context, non va bene is the natural Italian expression.

• non è bene is generally not used this way
• non è buona would mean it isn’t good, which sounds wrong for talking about size

When Italians talk about whether something is suitable, acceptable, or fits the situation, va bene / non va bene is the normal choice.

They are similar, but not identical.

• La misura non va bene focuses on the size itself not being right.
• Non mi sta bene focuses more on how the item fits me.

For example:

• La misura non va bene. = The size isn’t right.
• Non mi sta bene. = It doesn’t fit me well / It doesn’t suit me.

With clothing, stare bene is often used for how something looks or fits on a person.

Because Italian often drops subject pronouns when they are already clear from the verb form.

• posso already means I can
• so io is not necessary

You could say io posso, but that adds emphasis, like:

• Io posso fare un reso, ma lui no. = I can make a return, but he can’t.

In a neutral sentence, just posso is the normal choice.

Yes. Fare un reso means to make a return in a shopping context.

A reso is a return of a purchased item. This expression is especially common in retail, online shopping, and customer service language.

Other possible ways to say something similar are:

• fare un reso
• effettuare un reso = more formal
• restituire l’articolo = to return the item

One useful distinction:

• reso = the return process/action
• rimborso = refund

So a reso is not automatically the same thing as a refund, even though the two are often related.

Because the sentence is talking about making a return in a general sense, not referring to one already identified return.

• fare un reso = make a return
• fare il reso can also be heard, especially when the return is understood from context

Both can exist in real usage, but fare un reso is very natural when introducing the idea for the first time.

Entro domani means by tomorrow or no later than tomorrow.

The key word is entro, which expresses a deadline:

• entro stasera = by this evening
• entro lunedì = by Monday
• entro domani = by tomorrow

So the idea is that the return must be done before that time limit expires.

Because Italian often uses the present tense for a future action when the time reference is clear from context.

Here, entro domani already shows the future time frame, so posso sounds perfectly natural.

English does something similar:

• If the size doesn’t work, I can return it by tomorrow.

So this is present tense in form, but it refers to a future possibility.

In many clothing situations, yes, taglia would sound more specific and more idiomatic.

• taglia = clothing size
• misura = size/measurement, sometimes broader

So:

• Se la taglia non va bene, posso fare un reso entro domani.

may sound more natural if you are clearly talking about clothes or shoes.

But misura is still understandable, especially in a general shopping context.

The given order is very natural, but Italian does allow some flexibility.

Standard order:

• Se la misura non va bene, posso fare un reso entro domani.

You could also say:

• Posso fare un reso entro domani se la misura non va bene.

Both are correct. The version with se first sounds slightly more natural if you want to present the condition first.