If you run really heavy games on the 730 on max settings, It will drop below 60 fps, If you use the 855 it wont drop and will stay at 60 fps what so ever
This may be due to your sound settings, Go to Accessibility > Hearing > Mono Audio > Set it to off
If the problem isn't this try going to Settings > Sounds and Vibrations > Sound Quality and Effects > Set equilizer to Nornal
If none of this works It may just be the phone speakers dogy or thats...
If you visit Files then Internal Storage, Music or Internal Sorage, DCIM
These are where your files are, The problem is some are in the wrong fder as when you download wondershare it rebuilds your music and video databbase
Since your phone was released in 2015, Samsung have discontinued its software updates on that device since newer software such as nougat will not run due to your phone only having 1gb of ram, Your phone is locked to Android Kitkat