This is actually a really old theme (using my old coding method/layout) that was a giveaway and originally used at i-roleplay.
It is important you read the post in the live preview to understand how to get the semi-transparent sidebar. Instructions are there to help.
Please save and refresh the customize page before making any customizations/change. This will hopefully lower the number of problems. Feel free to customize however much you want, the more the better, but leave credits intact. It would also be great if you could ‘like’ this post if using the theme.