You mentioned that the error message includes Turkish characters, but your app.config does not.
If you take a look at the App.config file of your model (yes, your model's, not the application's App.config) you can chech and confirm that the connection string there matches the connection string in the App.config of your application. The connection string in the App.config of the model is automatically generated given the information you provided when creating your model, or later if you modified the model properties.
On a second note, I have created connection strings several using non-english characters and they all worked fine with the exception of Turkish characters. I have not found if there is something missing, but also have not found any documentation stating that Turkish characters are not supported in Visual Studio.
I suggest you first try not using Turkish characters, so we can eliminate that as a cause for not being able to connect. You can modify the DataSource key (as well as EntityManager Name, Entity Container Name, etc) in the properties of your edmx. (open your edmx file, right-click anywhere in the white area, and select Properties)