Hello Nenad,
Thank you for contacting Google Play Support. I understand you're having problems with country availability I can understand how this could be of concern, but I'll be more than happy to assist you with this today.
Thanks for writing in- we're excited to hear from our users from all over the world. At this moment, Google Play isn't available in Serbia. Please be assured that we are working hard to make Google Play available more widely, but since this requires a lot of negotiations with various teams (legal, content, etc.), I don't have an official timeline for when this might happen.
I'd also like to let you know to expect a short anonymous survey about your support experience in the next few days; we keep trying to find ways to improve our customer support, and your feedback will definitely help.
It was a pleasure speaking with you Nenad I hope I have been extremely helpful, and please don't hesitate to reply to this E-mail or contact us at support.google.com.
Regards,
Spencer
The Google Play Support Team