I think you all are already tired of the ones like me (with no clue about how to handle it),so please be patient and excuse me for maybe repeating same question like many before me.I downloaded books from amazon store and everything worked fine.But when I downloaded from other sites ( kindle mobi) the download worked fine and fast (through wi-fi ,directly to the device) I can`t open the files.I can't even move them anywhere in the device.

Any advice?What the problem might be and how to solve it?Thank you very much for you time and support.