Ακουμπάω την τσάντα μου στην καρέκλα και κάθομαι δίπλα στο παράθυρο.

Greek often leaves out subject pronouns because the verb ending already shows the person.
Here:

• Ακουμπάω = I put / I rest / I place
• κάθομαι = I sit / I am sitting

So εγώ is not necessary. You would only add εγώ if you wanted emphasis or contrast.

Ακουμπάω can mean several related things, such as touch, lean, rest, or put down gently. In this sentence, it means something like I put / I place / I set down my bag on the chair.

So the verb is broader than one single English verb, and the exact meaning depends on context.

Both are correct. Ακουμπάω and ακουμπώ are alternative present-tense forms of the same verb. A learner will hear both.

So:

• ακουμπάω την τσάντα = I put down my bag
• ακουμπώ την τσάντα = same meaning

The sentence uses Ακουμπάω, which is very natural.

Because τσάντα is the direct object of the verb Ακουμπάω. In Greek, a direct object takes the accusative case.

So:

• η τσάντα = the bag, as a subject
• την τσάντα = the bag, as an object

In this sentence, I am doing the action, and the bag is receiving the action, so Greek uses την τσάντα.

In Greek, possessive words like μου usually come after the noun.

So:

• η τσάντα μου = my bag
• το βιβλίο μου = my book
• η καρέκλα μου = my chair

That is the normal pattern. English puts my before the noun, but Greek usually puts μου after it.

Here μου means my.

It is the weak possessive form, and it matches English possessives like:

• μου = my
• σου = your
• του / της = his / her
• μας = our

So την τσάντα μου literally means the bag my, but in natural English it is my bag.

Στην is a contraction of σε + την.

So:

• σε = in, on, at, to
• την = the, feminine accusative singular
• στην = on/in/at/to the

Because καρέκλα is feminine, Greek uses την, and after contraction you get στην καρέκλα.

In this sentence, English says on the chair, but Greek uses σε for this kind of location.

Because the nouns have different genders.

• η καρέκλα is feminine, so σε + την = στην
• το παράθυρο is neuter, so σε + το = στο

So:

• στην καρέκλα = on the chair
• στο παράθυρο = at the window / to the window, depending on context

A very useful pattern is:

• στον for masculine
• στην for feminine
• στο for neuter

Very often, yes. Greek σε is broader than any one English preposition. The exact English translation depends on context.

For example:

• στο σπίτι = in the house / at home
• στο τραπέζι = on the table
• στο σχολείο = at school
• στον φίλο μου = to my friend

So στην καρέκλα is perfectly normal Greek even though English specifically says on the chair.

Δίπλα means next to / beside, and it is commonly followed by σε plus a noun phrase.

So:

• δίπλα στο παράθυρο = next to the window
• δίπλα στην πόρτα = next to the door

You may also hear δίπλα από, but δίπλα σε / στο / στην is very common and natural.

It has middle/passive-type endings, but here it has an active meaning: I sit or I am sitting. This is normal in Greek. Some verbs look passive in form but are active in meaning.

So κάθομαι is just the normal verb for I sit / I am seated.

You do not need to translate it as a passive in English.

Yes. The Greek present tense can describe:

• something happening now
• something someone does regularly

So depending on context, the sentence could mean either:

• I put my bag on the chair and sit next to the window
• I’m putting my bag on the chair and sitting next to the window
• a habitual action, such as what someone usually does in class

The surrounding context tells you which meaning is intended.

Yes, Greek word order is more flexible than English. The original sentence is a natural, neutral order, but other orders are possible if you want different emphasis.

For example, you could move δίπλα στο παράθυρο earlier or later. However, the basic grammar still stays the same:

• την τσάντα μου remains the object phrase
• στην καρέκλα and στο παράθυρο remain prepositional phrases
• the verb endings still show the subject

So the sentence is flexible, but the given version is a very normal way to say it.