- "beni" is accusative case for ben, "I" in english.
Do you miss me?; Beni özlüyor musun?
-"bunu" is the same again. accusative case for "bu", meaning "this".
-"bana" is the dative case of "ben"
Can you give this to me?; Bana bunu verebilir misin?
-"bizi" is accusative case of "biz", meaning "we".
Who called us?; Bizi kim aradı?
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The main difference between "Ahmet otomobili aldı" and "Otomobili Ahmet aldı" is the stress.
The word you want to emphsize must be next to the verb; in this case the verb is "aldı". In the first sentence "otomobil" is emphasized, in the latter "Ahmet".
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There is no word as "ayn" in Turkish. It might be aynı, which means "same".
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Seni ararken kendimi kaybediyorum.----> I lose myself while looking for you.
Seni; you (in accusative form)
ararken; while looking for (this part may be hard to understand for a beginner)
kendimi; myself (in accusative form). Kendi means "self", kendim means myself.
kaybediyorum; the verb is kaybetmek which literally means to make lost. It is made up from two words; kayıp (lost), etmek (to make, to do).
kaybet- is the root, -(i)yor- stands for present tense, -um stands for the conjugation of the verb according to the doer of the action; it is "ben" in this sentence.
I hope these help.