Ben de aynısını düşünüyorum.

Here de means too / also.

So Ben de... means I also... or Me too...

It is a separate word in this sentence, not a suffix.

• Ben düşünüyorum = I think
• Ben de düşünüyorum = I think so too / I also think

Yes. Turkish often drops subject pronouns because the verb ending already shows who is doing the action.

• Düşünüyorum already means I think / I am thinking
• So Ben de aynısını düşünüyorum could also be just Aynısını da düşünüyorum or Ben de öyle düşünüyorum, depending on context

But ben is often kept for emphasis, contrast, or clarity.

Here Ben de... can sound like:

• I do too
• I think the same too

So ben helps highlight I, especially if someone else has just said their opinion.

Good question. Turkish has two different de/da forms:

1. de/da as a particle meaning too / also

   • written separately
   • example: Ben de

2. -de/-da as a locative suffix meaning in / on / at

   • written attached
   • example: evde = at home

So in Ben de aynısını düşünüyorum, it is the also/too particle, so it must be written separately.

The particle changes by vowel harmony:

• after front vowels, use de
• after back vowels, use da

Since ben has the front vowel e, we get:

• ben de

Compare:

• O da geliyor. = He/She is coming too.
• Biz de biliyoruz. = We know too.

Aynısını is built from several parts:

• aynı = same
• -sı = third-person possessive marker
• -nı = accusative marker

So:

• aynısı = the same one / the same thing
• aynısını = the same one / the same thing as a direct object

In this sentence, aynısını düşünüyorum literally means something like:

• I am thinking the same thing
• I think the same

This structure is very common in Turkish.

Because düşünmek here is taking an object: the same thing.

Turkish usually needs that object to be expressed properly, and aynı by itself is just an adjective meaning same. It usually modifies a noun:

• aynı fikir = the same idea
• aynı şeyi = the same thing

When the noun is left implied, Turkish often uses a form like aynısı / aynısını to mean the same one / the same thing.

So:

• Ben de aynı düşünüyorum is not natural
• Ben de aynısını düşünüyorum is natural

A very close alternative is:

• Ben de aynı şeyi düşünüyorum = I’m thinking the same thing too

They are very similar.

• aynısını düşünüyorum = I think the same thing
• aynı şeyi düşünüyorum = I think the same thing

The second one is more transparent for learners because şey literally means thing.

Breakdown:

• aynı şeyi
  • aynı = same
  • şey = thing
  • -i = accusative

So both are correct, but aynısını düşünüyorum is a very natural compact way to say it.

It is the present continuous form:

• düşün- = think
• -üyor = present continuous
• -um = I

So literally it is I am thinking.

But in Turkish, the present continuous is often used where English would simply use the present tense for current opinions or immediate reactions.

So düşünüyorum here is best understood as:

• I think so too
• I think the same thing
• I agree

not necessarily I am in the middle of thinking right now in a literal sense.

Yes, very often in context it works like I agree.

Literally it means I think the same thing too, but in natural conversation that often functions as agreement.

Still, it is not a perfect one-to-one replacement in every situation. It specifically emphasizes having the same opinion or thought.

Yes, but they are close.

• Ben de aynısını düşünüyorum = I think the same thing too
• Ben de öyle düşünüyorum = I think so too / I think that way too

öyle is often a bit broader and can refer to that way / like that / so.

aynısını is more specifically the same thing.

In many conversations, both could work.

Yes. Turkish word order is flexible, though some orders sound more neutral than others.

The most neutral here is:

• Ben de aynısını düşünüyorum.

But you may also hear:

• Aynısını ben de düşünüyorum.
• Ben aynısını da düşünüyorum. (less likely unless the meaning is slightly different in context)

Changing word order changes emphasis more than core meaning.

For example:

• Aynısını ben de düşünüyorum emphasizes the same thing
• Ben de aynısını düşünüyorum is a straightforward neutral response

A rough pronunciation is:

• ai-nuh-suh-nuh

More carefully:

• ay as in English eye
• nı has the Turkish ı, a vowel that does not exist in English exactly
• sı also has ı

The Turkish ı is a close back unrounded vowel. A simple learner tip: it sounds somewhat like the vowel in the second syllable of sofa, but not exactly.

So:

• aynısını ≈ eye-nuh-suh-nuh

That is only approximate, but it helps.

It is neutral and works in both formal and informal situations.

You can say it:

• to a friend
• in a meeting
• in ordinary conversation

It is polite and natural. It does not sound slangy.

You can try, but the result sounds awkward in English.

A rough literal breakdown is:

• Ben = I
• de = too
• aynısını = the same thing
• düşünüyorum = I am thinking

So literally: I too am thinking the same thing.

That helps with grammar, but in natural English the best translation is usually something like:

• I think so too.
• I think the same thing.
• I agree.

The best choice depends on context.