Text background disappears when text wraps MusicPlus theme

Thanks for a beautiful theme.

I have the problem that when I view my site on mobile devices or by if I manually resize my viewing window to a point where the text begins to wrap, the white area behind my text disappears. This whould not be a big problem in mormal circumstances but for me it's a problem because I have a dark background image and this makes it impossible to read the text once this happens.
I tried to solve the problem by disabling responsiveness but this did not solve the problem.

Here is my the website: me-afrika.de

Does anyone have any ideas how I can overcome this problem? Thanks in advance.