Switching theme will mess up formatting?

Hi,

I want to switch from my current theme to a twenty-fourteen theme to check if the frequent 500 Internal Server Error popping up on my website will be fixed.

But I’m scared that this will mess up the formatting-I know it will be messed up when I switch to twenty-fourteen. What I want to know is will it be messed up or changed after switching back again to the current one I’m using?

Thanks for the help!