Ben peçeteyi çöp kutusuna attım.

Yes. In Turkish, subject pronouns are often omitted because the verb already shows the person.

• attım already means I threw
• the -m at the end marks first person singular

So Peçeteyi çöp kutusuna attım is perfectly natural.
Using ben adds emphasis, contrast, or clarity, like I threw the napkin.

Because peçeteyi is the definite direct object.

In Turkish, when the object is specific or known, it usually takes the accusative ending.

• peçete = a napkin / napkin in general
• peçeteyi = the napkin / that napkin

So this sentence is talking about a specific napkin, not just any napkin.

It is the accusative case ending, which marks a specific direct object.

The basic accusative suffix is one of:

• -ı
• -i
• -u
• -ü

Which one appears depends on vowel harmony. After a vowel, Turkish often adds a buffer letter y, so:

• peçete + i becomes peçeteyi

That y is there only to make pronunciation smoother.

Because çöp kutusu is a very common Turkish noun compound.

Turkish often builds nouns like this:

• çöp = trash, garbage
• kutu = box, container
• çöp kutusu = trash can, garbage bin

In these compounds, the second noun usually takes a special ending, often called the compound marker or third-person possessive-looking ending.

Other examples:

• yatak odası = bedroom
• otobüs durağı = bus stop
• kahve fincanı = coffee cup

So çöp kutusu is just the normal Turkish way to say trash can.

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

Here it shows the direction of the action:

• çöp kutusuna = to the trash can / into the trash can

The form is -na instead of just -a because çöp kutusu already ends in that compound/possessive-style ending -su. After such endings, Turkish often inserts a buffer n before another case ending.

So:

• çöp kutusu
• çöp kutusu + a
• becomes çöp kutusuna

attım breaks down like this:

• at- = throw
• -tı = past tense
• -m = I

So:

• at + tı + m = attım = I threw

The double tt appears because the verb stem already ends in t, and the past suffix also begins with t here.

Because of consonant assimilation.

The past tense suffix is basically -dı / -di / -du / -dü, but after a voiceless consonant it changes to -tı / -ti / -tu / -tü.

Since at- ends in t, which is voiceless, the suffix becomes -tı.

So:

• at- → attı

Then adding -m gives attım.

Because of vowel harmony.

Turkish chooses the vowel in many suffixes according to the last vowel of the stem.

The last vowel in at- is a, so the first-person ending becomes -ım rather than -im.

That gives:

• attı + m → attım

So the dotless ı is the correct vowel here.

Not completely. The neutral, standard order is:

• Ben peçeteyi çöp kutusuna attım.

This is basically Subject + Object + Place/Direction + Verb.

But Turkish word order is flexible, especially for emphasis or topic/focus. For example:

• Peçeteyi çöp kutusuna attım.
• Ben çöp kutusuna peçeteyi attım.

These can all be grammatical, but the emphasis changes. In ordinary neutral speech, keeping the verb at the end is most common.

Yes, absolutely.

• çöpe attım = I threw it in the trash / I threw it away
• çöp kutusuna attım = I threw it into the trash can

The version with çöp kutusuna is more specific because it names the container directly.
The version with çöpe is shorter and very common in everyday speech.

Yes. -dı / -di / -du / -dü is the simple past and normally refers to a completed event.

So attım presents the action as something that happened and is finished. In English, it is usually translated as I threw. Depending on context, English might sometimes prefer I have thrown, but the basic Turkish form is a completed past action.