Ben çantayı kapının önüne koyuyorum.

Yes. Turkish often drops subject pronouns because the verb ending already shows the person.

• koyuyorum = I am putting
• So Ben çantayı kapının önüne koyuyorum and Çantayı kapının önüne koyuyorum both mean I am putting the bag in front of the door.

Including ben adds emphasis or contrast, like:

• Ben koyuyorum, o değil. = I’m putting it, not him/her.

Because it is the definite direct object of the verb.

• çanta = bag
• çantayı = the bag

The ending -yı is the accusative case here. Turkish usually marks a direct object with the accusative when it is specific or definite.

Compare:

• Çanta koyuyorum. = I’m putting a bag / bags
• Çantayı koyuyorum. = I’m putting the bag

The y is a buffer consonant added because the noun ends in a vowel:

• çanta + ı would be awkward
• so Turkish uses çanta + yı

Kapının means of the door.

• kapı = door
• kapının = of the door / the door’s

The ending -ın is the genitive case. It is used because Turkish often expresses relationships like the front of the door, the handle of the door, etc., with a genitive construction.

So:

• kapının önü = the front of the door
• literally: the door’s front

Because the sentence means to in front of the door, showing direction.

Break it down:

• ön = front
• önü = its front / the front of it
• önüne = to its front / to in front of it

In this sentence, kapının önüne means to the area in front of the door.

The ending -e is the dative case, which often means to, toward, or into a place.

So:

• kapının önü = the front of the door
• kapının önünde = at/in front of the door
• kapının önüne = to in front of the door

This is a very common and important distinction.

• kapının önüne = to in front of the door → movement toward that place
• kapının önünde = in front of the door → location, no movement

With koymak (to put/place), Turkish usually uses the dative because you are placing something to a location:

• Çantayı kapının önüne koyuyorum. = I’m putting the bag in front of the door.

But with a stative verb:

• Çanta kapının önünde. = The bag is in front of the door.

That n is a buffer consonant.

The form comes from something like:

• önü = its front
• plus -e = to

When Turkish adds a case ending after a 3rd-person possessed form like önü, it often inserts n:

• önü → önüne
• üstü → üstüne
• arkası → arkasına

So the n helps connect the possessed form to the case ending.

It behaves a bit like both, which can feel unusual to English speakers.

Words like ön, arka, üst, alt, iç, dış, yan are often body-part-or-space nouns that Turkish uses in location expressions.

Examples:

• evin önü = the front of the house
• masanın üstü = the top of the table
• kapının arkası = the back of the door

So kapının önüne is literally something like to the door’s front.

In natural English, we translate it as in front of the door.

Koyuyorum means I am putting / I’m placing.

It comes from:

• koymak = to put, to place
• verb stem: koy-
• progressive marker: -yor
• 1st person singular ending: -um

So:

• koy-yor-um → koyuyorum

The extra u appears for pronunciation and spelling reasons. This is the normal form.

Examples:

• koyuyorum = I am putting
• koyuyorsun = you are putting
• koyuyor = he/she/it is putting

Usually it means an action in progress, like I am putting or I’m placing. In many contexts, that is the best translation.

But the Turkish -yor form can sometimes also be used more broadly depending on context, for example for a current ongoing situation or near-future meaning.

In this sentence, the most natural reading is:

• I am putting the bag in front of the door.

Turkish word order is often Subject – Object – Location – Verb, with the verb commonly at the end.

So:

• Ben = I
• çantayı = the bag
• kapının önüne = in front of the door
• koyuyorum = am putting

Literally:

• I the bag to the front of the door am putting

Natural English:

• I am putting the bag in front of the door.

Turkish word order is flexible, but the verb very often stays at the end.

Yes, very natural:

• Çantayı kapının önüne koyuyorum.

That is probably the more neutral version in everyday Turkish if there is no need to emphasize I.

Because the bag is not being put to the door itself. It is being put to the front of the door.

Compare:

• kapıya = to the door
• kapının önüne = to in front of the door

These are different meanings.

Examples:

• Kapıya gidiyorum. = I’m going to the door.
• Çantayı kapının önüne koyuyorum. = I’m putting the bag in front of the door.

Yes. Koymak is a very common verb that often means:

• to put
• to place
• sometimes to set down

In this sentence, all of these could work depending on style:

• I’m putting the bag in front of the door.
• I’m placing the bag in front of the door.

Put is the most natural everyday choice.