Παραδέχομαι ότι έκανα λάθος και ότι έπρεπε να είχα απαντήσει νωρίτερα.

Because the speaker is making the admission now.

• Παραδέχομαι = I admit / I’m admitting
• What follows after it is the content of that admission:
  • ότι έκανα λάθος = that I made a mistake
  • ότι έπρεπε να είχα απαντήσει νωρίτερα = that I should have answered earlier

So the sentence combines a present-time speech act with past events.

Greek usually drops subject pronouns when they are not needed.

The ending -ομαι already tells you the subject is I here:

• παραδέχομαι = I admit
• παραδέχεσαι = you admit
• παραδέχεται = he/she/it admits

You could say Εγώ παραδέχομαι if you want emphasis, contrast, or emotional force, but it is not necessary in a neutral sentence.

Because some Greek verbs have middle/passive morphology but an active meaning.

So:

• παραδέχομαι does not mean I am admitted
• it means I admit / I acknowledge

This is very common in Greek. Learners often notice the -ομαι ending and expect a passive meaning, but many verbs simply work this way.

Both clauses depend on Παραδέχομαι, so repeating ότι makes the structure clear and balanced:

• Παραδέχομαι ότι έκανα λάθος
• και ότι έπρεπε να είχα απαντήσει νωρίτερα

In English, repeating that is optional in many cases, and the same is often true in Greek. You could also hear:

• Παραδέχομαι ότι έκανα λάθος και έπρεπε να είχα απαντήσει νωρίτερα.

That is also natural. Repeating ότι just makes the sentence a bit more explicit.

No.

• ότι = that
• ό,τι = whatever / anything that / what

In this sentence, it is ότι because it introduces a content clause after Παραδέχομαι.

So here:

• Παραδέχομαι ότι... = I admit that...

Not:

• Παραδέχομαι ό,τι... = I admit whatever... which would mean something very different.

Yes, more or less. κάνω λάθος is a very common Greek expression meaning:

• I make a mistake
• I am mistaken
• I am wrong

So:

• έκανα λάθος = I made a mistake / I was wrong

Greek often uses this expression where English might prefer I was wrong.

Also, Greek often leaves out the article here:

• έκανα λάθος is much more idiomatic than έκανα ένα λάθος in many contexts.

Έκανα is the aorist, which presents the mistake as a completed past event.

So:

• έκανα λάθος = I made a mistake / I was wrong

If you said:

• έχω κάνει λάθος

that would mean I have made a mistake, with a stronger link to the present result.

And while έκανα ένα λάθος is grammatically possible, έκανα λάθος is the more standard idiomatic expression in this kind of sentence.

This is a very common Greek way to express past obligation/regret.

Break it down:

• έπρεπε = imperfect of πρέπει, literally it was necessary / I was supposed to
• να είχα απαντήσει = roughly to have answered / had answered

Together:

• έπρεπε να είχα απαντήσει = I should have answered

It implies that the action did not happen when it should have.

You can say that, but the nuance is a bit different.

• έπρεπε να απαντήσω νωρίτερα = I was supposed to answer earlier / I should answer earlier
• έπρεπε να είχα απαντήσει νωρίτερα = I should have answered earlier

The version with να είχα απαντήσει more clearly points to an unfulfilled past action and often sounds more like regret or self-criticism.

So in this sentence, έπρεπε να είχα απαντήσει νωρίτερα is especially suitable.

It comes from the verb:

• απαντώ / απαντάω = I answer / reply

The form απαντήσει is the form used in perfect-type constructions with έχω / είχα:

• έχω απαντήσει = I have answered
• είχα απαντήσει = I had answered

So in:

• να είχα απαντήσει

it is part of the construction meaning to have answered / had answered.

A simple way to think of it is: it is the verb form Greek uses after έχω / είχα to build meanings like have answered or had answered.

Νωρίτερα means earlier / sooner.

It is the comparative adverb related to νωρίς = early.

So:

• νωρίς = early
• νωρίτερα = earlier

You can also say:

• πιο νωρίς

and it means almost the same thing. Both are natural. In this sentence, νωρίτερα sounds very normal and compact.

Greek word order is fairly flexible, but the version given is neutral and natural.

The original sentence:

• Παραδέχομαι ότι έκανα λάθος και ότι έπρεπε να είχα απαντήσει νωρίτερα.

sounds balanced and straightforward.

You could move things around for emphasis, but not every rearrangement sounds equally natural. For example, putting νωρίτερα earlier might add emphasis to earlier, and using εγώ could add contrast. Still, the original order is the safest and most idiomatic choice for a learner.

Because the sentence joins two fairly full clauses:

• ότι έκανα λάθος
• ότι έπρεπε να είχα απαντήσει νωρίτερα

In Greek, a comma before και is often not used in short simple coordination, but it can appear when the clauses are longer or when the writer wants to separate them more clearly.

So here the comma helps readability, but in less formal writing you may also see the sentence without it.