Translation - Turkish-English - SEVGİLİ ARKADAŞIM, SEN GİTTİĞİNDEN BERİ BURALAR...

You're mixing up present tense and present perfect tense here. Here's how it should read:

My dear friend,
Since you've been gone, it has been very boring around here.
I have begun to miss you quite a lot.
There are no good friends like you around here at all.
I long for you a lot, no one can take your place.
I could not even feel happy that it was summer holiday because you were not here
I hope the holiday passes quickly
See you.

Yes you are right I mixed them up. Thanks