Check the Bluetooth connectivity on your phone to see if it's fully connected. If it's not connected correctly turn of the phone and the speaker and turn it back on then connect the Bluetooth again. Make sure both the phone and speaker are synced properly before playing music.
To improve the volume of the speaker; reset the speakers to see if the volume is working well again. If the speaker is not completely responding check to see if the sound button is broken, if it is broken replace it.