Indago da solo.

Indago is the first-person singular present indicative of indagare.

So it means:

• I investigate
• I am investigating

Italian uses the simple present much more broadly than English, so the exact English tense depends on context.

Italian often drops the subject pronoun because the verb ending already shows who is doing the action.

• indago = I investigate / I am investigating

So Indago da solo is perfectly natural.

You can say Io indago da solo, but adding io usually gives extra emphasis, such as:

• I investigate on my own
• As for me, I investigate on my own

Da solo means by myself / on my own / alone.

In this sentence, it tells you how the action is done: the speaker investigates without other people helping or accompanying them.

It is a very common Italian expression.

Because da solo is the clearest way to say on one’s own / by oneself.

If you say solo, it can sometimes be ambiguous, because solo can also mean only.

Compare:

• Indago da solo = I investigate on my own
• Indago solo = more likely I only investigate

So da solo is the safer and more natural choice here.

Yes. Solo agrees with the person or people being described.

Forms:

• da solo = masculine singular
• da sola = feminine singular
• da soli = masculine plural or mixed plural
• da sole = feminine plural

So a woman would say:

• Indago da sola.

A group of women would say:

• Indaghiamo da sole.

It is a normal Italian verb, but it sounds a bit more formal or serious than many everyday verbs.

It is especially common in contexts like:

• police investigations
• journalism
• legal matters
• formal inquiry
• detective-style language

In casual everyday speech, depending on the situation, Italians might also use expressions such as:

• cerco di capire da solo = I try to figure it out by myself
• faccio ricerche da solo = I do research on my own
• mi informo da solo = I find out for myself

So indago is correct, but it has a somewhat more investigative tone.

Because the h is only needed before e or i to keep the hard g sound.

With o, the hard g is already natural, so no h is needed:

• indago
• indagano

But:

• indaghi
• indaghiamo

This is the normal spelling pattern for -gare verbs in Italian.

It can mean either, depending on context.

So Indago da solo could suggest:

• the speaker investigates without anyone else present
• the speaker investigates without help
• or both

In many real situations, da solo often carries the sense of on my own, not necessarily just physically alone.

Yes, but Indago da solo is the most neutral and natural order.

Other possibilities:

• Io indago da solo = same basic meaning, but with emphasis on io
• Da solo indago = possible, but marked or literary
• Indago solo = usually changes the meaning to I only investigate

So for a learner, Indago da solo is the best standard version.