Help!

Hi guys, I hope it's okay to ask this in here.

I took some ugly pictures with a mobile and some of them (actually, almost all of them) look REALLY dark.
Here's an example:


So, if I try something simple like screen, the picture looks this way:


Yep, bad.

I haven't had this problem before so I don't know if there's a way to make them look good.

Any ideas to make them look better?