Όταν γύρισα σπίτι, βρήκα τον μικρό να κάθεται στο χαλί με το αρκουδάκι, το μπλοκ και τις κηρομπογιές του, και τότε ξέχασα όλη την κούραση της μέρας.

Here Όταν means when in a time sense: when I got home / when I returned home.

It introduces a time clause:

• Όταν γύρισα σπίτι = When I came back home

It is not conditional here. It simply sets the scene for what happened next.

Γύρισα is the aorist form, which presents the action as a single completed event:

• γύρισα = I came back / I returned

If you said γύριζα, that would usually suggest an ongoing, repeated, or background action:

• γύριζα σπίτι could mean something more like I was going back home or I used to return home

In this sentence, the speaker is referring to one completed moment: when I got home. So γύρισα is the natural choice.

In Greek, σπίτι after verbs like πηγαίνω, έρχομαι, γυρίζω can work a bit like an adverbial destination:

• γύρισα σπίτι = I returned home
• πάω σπίτι = I’m going home

This is very common and natural.

If you say στο σπίτι, that usually means to the house/home more explicitly, with the noun fully expressed as the destination:

• γύρισα στο σπίτι = also correct, slightly more explicit

So:

• γύρισα σπίτι = very natural, compact
• γύρισα στο σπίτι = also fine

Yes. τον μικρό literally means the little one or the little boy.

The adjective μικρός is being used like a noun:

• ο μικρός = the little one / the young one / the little boy
• τον μικρό = accusative form, because it is the object of βρήκα

So:

• βρήκα τον μικρό = I found the little one / the boy

In family or everyday speech, ο μικρός very often means the child, especially the young son or the little boy.

Because it is the direct object of the verb βρήκα.

• βρήκα = I found
• Who did I find? τον μικρό

Greek marks the direct object with the accusative:

• nominative: ο μικρός
• accusative: τον μικρό

So βρήκα ο μικρός would be ungrammatical.

This is a very common Greek structure after verbs like βλέπω, ακούω, βρίσκω, etc.

• βρήκα τον μικρό να κάθεται = I found the little one sitting
• more literally: I found the little one to be sitting

The να + verb part describes what the person was doing at that moment.

Compare:

• Τον είδα να τρέχει. = I saw him running.
• Τον βρήκα να κοιμάται. = I found him sleeping.

So in your sentence, να κάθεται explains the state/action the child was in when the speaker came home.

Because κάθεται is the imperfective form, which shows an action in progress:

• να κάθεται = to be sitting / sitting

This fits the meaning: the child was already there, in that ongoing state.

If you used να καθίσει, that would be perfective and would suggest something more like to sit down, focusing on the action as a whole or as a single event. That would not fit well here.

So:

• βρήκα τον μικρό να κάθεται = I found him sitting
• not I found him to sit down

Normally, after να, Modern Greek uses the subjunctive form:

• να κάθεται

You would not normally say να καθόταν here.

The difference is:

• κάθεται = present/imperfective form
• καθόταν = past imperfect, meaning he was sitting

In this structure after βρήκα, Greek uses:

• να + present imperfective to express the ongoing action at that moment

So:

• βρήκα τον μικρό να κάθεται = correct
• βρήκα τον μικρό καθόταν = incorrect
• βρήκα τον μικρό να καθόταν = not the normal standard structure here

στο is a contraction of:

• σε + το = στο

So:

• στο χαλί = on the rug / carpet

With σε, Greek often uses it for location, and in English you may translate it as in, at, or on depending on the noun and context.

Here:

• κάθεται στο χαλί = he is sitting on the rug

Because one με can govern the whole list.

So:

• με το αρκουδάκι, το μπλοκ και τις κηρομπογιές του means
• with his teddy bear, his pad/block, and his crayons

Greek does not need to repeat με before every item, just like English usually does not repeat with in a simple list.

Αρκουδάκι means little bear, and in context usually teddy bear.

The ending -άκι is a very common diminutive ending in Greek. It often adds a sense of:

• small size
• affection
• cuteness

So:

• αρκούδα = bear
• αρκουδάκι = little bear / teddy bear

In children’s contexts, this is extremely natural.

Here το μπλοκ usually means a pad, such as a drawing pad or notebook pad.

It is a loanword, and Greek uses many such words naturally in everyday speech. In this sentence, because the child also has crayons, το μπλοκ probably means a drawing pad / sketch pad / notebook pad.

τις κηρομπογιές του means his crayons.

Breakdown:

• τις κηρομπογιές = the crayons (accusative plural)
• του = his

So του refers back to τον μικρό, the child.

Greek often uses the weak possessive pronoun after the noun:

• το βιβλίο μου = my book
• οι φίλοι της = her friends
• τις κηρομπογιές του = his crayons

In context, yes, it very likely applies to the whole group:

• his teddy bear, his pad, and his crayons

Greek often places the possessive only once, especially when it is clear that it belongs with the whole list.

So the sentence strongly suggests that all these items are the child’s things, even though του appears only after the last noun.

και τότε means and then or and at that moment.

It marks the emotional result of what the speaker saw:

• first, the speaker came home
• then saw the child sitting there with his things
• and then forgot all the day’s tiredness

So τότε helps show the transition from the scene to the emotional reaction.

Ξέχασα is aorist, so it presents the forgetting as a single completed reaction:

• I forgot

This matches the idea of a sudden emotional shift:

• I saw him, and at that moment, I forgot all my tiredness.

Ξεχνούσα would suggest an ongoing or repeated process:

• I was forgetting which does not fit as well here.

Because κούραση is a feminine noun, and the phrase is in the accusative singular as the object of ξέχασα.

Forms of όλος here:

• nominative feminine: όλη
• accusative feminine: όλη
  (same form in this case)

So:

• όλη την κούραση = all the tiredness / all the fatigue

Greek often uses όλος with the article:

• όλη την κούραση
• όλο το βιβλίο
• όλον τον κόσμο

Yes, this is a genitive phrase expressing what kind of tiredness it is:

• η κούραση της μέρας = the tiredness of the day
• more naturally in English: the day’s tiredness or the tiredness of the day

So:

• όλη την κούραση της μέρας = all the day’s tiredness / all the tiredness of the day

Greek uses the genitive very often where English uses of or an apostrophe structure.

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

The sentence moves in a very smooth sequence:

1. Όταν γύρισα σπίτι — time/background
2. βρήκα τον μικρό να κάθεται... — what the speaker saw
3. και τότε ξέχασα... — emotional result

Some parts could be rearranged, but the original sounds very natural for narration. Greek often uses word order to shape emphasis and flow, not just grammar.

Because Όταν γύρισα σπίτι is an introductory subordinate clause:

• When I got home, ...

Greek, like English, commonly separates that opening time clause with a comma before the main clause:

• Όταν γύρισα σπίτι, βρήκα...

This helps readability and reflects the sentence structure clearly.