Scale the Lightbox to 90-95% height?

Hello everybody,

first of all I would like to thank you for this wonderful theme! The first one which has everything what I need directly included except one thing, which I suppose is not included in no theme (leaguemanager) 😉

I only have one problem with the lightbox, which I can’t solve. I want the lightbox to scale to the height and maybe also to the width (for iPhone maybe?), because at the moment my images are way to big to look on a normal screen. But i don’t want to downscale them via Photoshop, because I don’t know which max. size I should take.

I already tried to change the video/image in the style.css, but this chances also the images in the posts I suppose.
In the colorbox.css I also tried to chance various different things, but I didn’t reach my goal.

So how can I make the lightbox fitting in my Screensize (Computer and iPhone)?

Thank you a lot 🙂

Here is the Website:
And here a sample post with image: