Questa condizione migliora con il riposo.

Because condizione is a feminine singular noun in Italian, so the demonstrative must match it.

• questo = this, masculine singular
• questa = this, feminine singular

So:

• questa condizione = this condition

Agreement like this is very important in Italian.

Migliora is the third-person singular present tense of the verb migliorare, meaning to improve or to get better.

Here it agrees with questa condizione, which is singular:

• la condizione migliora = the condition improves / is improving / gets better

In Italian, the present tense often covers several English possibilities depending on context:

• improves
• is improving
• does improve
• sometimes even gets better

Italian usually does not use subject pronouns unless they are needed for emphasis or clarity.

So instead of saying:

• Essa migliora con il riposo

Italian normally just says:

• Questa condizione migliora con il riposo

Or, if the subject is already clear from context:

• Migliora con il riposo

This is different from English, where you usually need to say it.

Here con literally means with, and in this context it expresses the idea of improvement occurring thanks to or during rest.

So:

• migliora con il riposo = improves with rest

English sometimes uses with, from, or after depending on style, but Italian naturally uses con here.

Similar examples:

• Il dolore passa con il tempo = The pain goes away with time
• Migliora con la terapia = It improves with therapy

Italian often uses the definite article where English would use no article.

So:

• con il riposo literally = with the rest
• natural English = with rest

This is very common in Italian, especially with general concepts, body parts, and abstract nouns.

Compare:

• con il tempo = with time
• ha la febbre = he/she has a fever
• mi fa male la testa = my head hurts

So il riposo is completely normal here.

No, that would not be natural here.

The correct form is:

• Questa condizione migliora con il riposo

The verb migliorare can be used in different ways, but in this sentence the condition itself is the thing that improves, so the simple form works best.

• La situazione migliora = The situation improves
• La salute migliora = Health improves

Using si migliora usually changes the meaning and often refers more to one improves oneself or appears in other structures, not this one.

Yes. In English, both are good translations depending on style.

• Questa condizione migliora con il riposo
  = This condition improves with rest
  = This condition gets better with rest

Improves sounds a little more formal or medical.
Gets better sounds a little more everyday and conversational.

In Italian, migliora can cover both ideas.

The standard, neutral order is:

• Questa condizione migliora con il riposo

That is the most natural order for a simple statement.

You could change the order for emphasis, for example:

• Con il riposo, questa condizione migliora

This puts more focus on con il riposo. It is still correct, but less neutral.

So yes, the word order can change, but the original version is the most straightforward.

A rough pronunciation guide:

• questa ≈ KWEH-sta
• condizione ≈ kon-dee-tsyoh-neh
• migliora ≈ meel-YOH-ra
• con il riposo ≈ kon eel ree-POH-zo

A couple of useful pronunciation notes:

• gli in migliora is a special Italian sound, similar to the lli in some pronunciations of million, but more distinctly Italian.
• zione in condizione sounds like tsyoh-neh.

If you want to sound natural, stress is important:

• condiZIÓne
• miglioRA
• riPÓso

The main dictionary forms are:

• questa ← from questo = this
• condizione = condition
• migliora ← from migliorare = to improve / to get better
• con = with
• il = the
• riposo = rest

It is useful to learn nouns with gender:

• la condizione = the condition
• il riposo = the rest

And verbs in the infinitive:

• migliorare = to improve

Yes, very natural. It sounds like something you could read or hear in a medical or health-related context.

For example, a doctor or leaflet might say:

• Questa condizione migliora con il riposo.

It is clear, neutral, and idiomatic.
If you wanted a slightly more formal version, Italian might also use:

• Questa condizione tende a migliorare con il riposo.
  = This condition tends to improve with rest.

But the original sentence is already perfectly natural.