Learn Hardcore Greek: Αν κάνω σφάλμα στο email, θα το διορθώσω αμέσως. - If I make a mistake in the email, I will correct it immediately.

Αν means if and introduces a condition. In this sentence it sets up a possible situation: If I make a mistake in the email...
You can also see εάν in more formal Greek; it means the same as αν.

Is κάνω here present tense (“I am doing/making”), or something else?

Formally, in a future-type condition after αν, Greek uses a subjunctive-like form (often called “dependent” or “conditional” use), but κάνω looks identical to the present indicative κάνω. Practically, you can understand αν κάνω as if I (happen to) make.

Why is there no να after αν? I thought subjunctive needs να.

You’re right that Greek often marks the subjunctive with να (e.g., να κάνω). But after αν (and after όταν in some uses), Greek typically does not use να. So αν κάνω is normal and means if I do / if I make in this conditional sense.

What does θα do in θα το διορθώσω?

Θα is the particle that forms the future (and some other modal meanings).
So θα ... διορθώσω = I will correct ...

Why is it διορθώσω and not διορθώνω?

Διορθώσω is the perfective (often “aorist-based”) form used after θα to express a single completed action: I’ll correct it (once, successfully).
Θα διορθώνω would usually imply something more ongoing/repeated (like “I’ll be correcting / I’ll correct regularly”), which doesn’t fit as well with αμέσως (immediately).

What is το in θα το διορθώσω? Why is it there?

Το is an object pronoun meaning it (neuter singular). It refers back to σφάλμα (mistake/error), which is neuter: το σφάλμα.
So θα το διορθώσω = I’ll correct it.

Where does το go in Greek word order? Can it move?

With a simple future like this, the object pronoun normally goes between θα and the verb:

θα το διορθώσω (standard)

You generally wouldn’t put it after the verb in normal neutral speech (that’s more common with imperatives or special emphasis).

Why is it στο email and not σε το email?

στο is just a contraction of σε + το:

σε το email → στο email

This is extremely common in everyday Greek.

Does στο email mean “in the email” or “by email”?

Here στο email most naturally means in the email (message)—i.e., a mistake inside what you wrote.
If you mean “by email” (as a method of communication), Greek would typically use something like με email or μέσω email depending on context.

Is σφάλμα the same as λάθος? Why use σφάλμα?

Both can mean mistake, but there’s a nuance:

λάθος is the most common everyday word for “mistake/wrong thing.”
σφάλμα can sound a bit more formal/technical (like “an error”), and it’s also common in writing.

So σφάλμα στο email sounds slightly more formal than λάθος στο email, but both are possible.

Why is there a comma: Αν κάνω σφάλμα στο email, θα το διορθώσω αμέσως.?

It separates the if-clause from the main clause, just like in English:
If ... , I will ...
In Greek, this comma is very standard when the conditional clause comes first.

What does αμέσως modify, and where can it go?

Αμέσως means immediately/right away and modifies θα το διορθώσω (the correcting).
It often appears at the end, but you can also place it earlier for emphasis, e.g.:

... θα το διορθώσω αμέσως. (neutral/common)
... θα το διορθώσω αμέσως, μην ανησυχείς. (adds reassurance)
... θα το διορθώσω αμέσως. vs ... θα το διορθώσω αμέσως εγώ. (emphasis on who)