Spotify background problem.

[redesterspotify]

I have spotify running on android 4.4.2. Is it normal that when i have it on backround it silences all the other apps? I mean, if i receive a call i cant listen even if spotify stops playing music. same thing with other apps like radio app or music app. they runs but no music. i have t kill spotify and than i can listen. 

another thing is spotify desktop. it says no connection but im perfectly connected on the web. may be a port problem , if i change router it works. how can i set my router to open the port? thanks