Wifi, bluetooth and locked screen problems

Yesterday my iPhone started behaving a bit weird, the volume would turn down when getting for example a message on FB or an email, and it would stay down until I would close the program which gave the notification. Today I first had a problem that my iPhone would freeze, so I locked the screen but I couldn't unlock it anymore, it only vibrated when I muted the sound but except for that it wouldn't respond to anything. To fix this I did a reset (home button+screenlock button) and it worked, but my wifi button went dark and I couldn't activate it anymore, bluetooth also isn't working (the loading circle just keeps on spinning) and to make it even better, when my iPhone has the locked screen without playing music, it freezes on the locked screen after a couple of minutes, only the reset works. I tried to make a back up of my iPhone, but it would lose connection while syncing when moved..... After a couple of attempts I managed to make a back up and reset all settings on my iPhone (it didn't help). I haven't succeeded yet in getting a proper restoration from the back up file (programs are missing), but after I couple attempts I managed to install iOS 8.4 (before that I had 8.3), but it didn't fix the problem. It's an iPhone 6 64GB without any forms of jailbreak.