For what it's worth: https://instagram.apk.cafe/prestigio/muze-b7 says it's meant for your phone so should work.
If no luck, go back to factory conditions and start all over to see if you can get it working with the standard instagram app.
If still no luck, either something is wrong with the phone (such as having Marshmallow only, or an hardware issue), or it isn't a quality phone at all.
Hey guys I need your help and I hope this topic belongs here. So I have prestigio muze b7 and it's qualit phone but when I wanna watch instagram stories the stories bug exactly video froze and voice is going so I have to hold it but it's not working everytime and it makes me so mad