Last night you forgot you phone here

Thank youuuuuuuuu

 Dun gece senin cep telefonun burada býraktýn

My attempt

Dün gece burada telefonunu unuttun.

almost completely correct

the same

but I would never use "senin" here, although it is not wrong.

another comment, we would more often say here "býrakmýþsýn", because it was probably forgotton by mistake; so when he left, he didn´t realize, that´s learnt later. so we use "miþ" tense. But it is OK to use "býraktýn" as well.

   .....I speak very good English you know!  (only joking - your corrections are extremely helpful!)

1. Dun gece telefonunu burada biraktin

2. Dun gece telefonunu burada birakmissin.

These two sentences above may look similar, but in correct Turkish they are not alternatives. In fact, they belong to two different tenses and carry different meanings. The difference between these two sentences is that,

In (1),  the speaker is talking from a first hand experience, ie. the speaker was there when the telephone was left behind,  he spotted the incident with his own eyes after departure of his friend; his reporting to the owner of the telephone now  goes "You left your telephone here last night"..

In (2),  the situation is somewhat different; the speaker was probably not there when the telephone was left behind, or he himself was not the one to notice the incident after the departure of the guest. He is  now informing the telephone owner  based on information provided by a third party. Roughly translated it would correspond to "the word is  (or, it has been brought to my attention)  that you have left your telephone here last night".

Is this ´pick on Dilliduduk week´?? 

Thank you for your explanation Alpha but I think Dilliduduk told me basically the same thing and she just said it was okay to use ´biraktýn´ - meaning that the sentence would be understood although not strictly grammatically correct.  However, as we don´t know the situation behind the sentence, who is to say it wasn´t - and maybe your first scenario above is the correct one?