After editing the code and save, nothing is changing. Why?

Hi;
Thank you for the plugin.

My questions :
1) I m working at local environment and I am trying to change something at one of the plugins that I use. When I locate the code by using your plugin and make the change at your code editor and hit the save changes button at right handside, It does not make the change.

then I turn back to your code editor to check if it save it or not; I see that the code turns back its previous state.

2) At your plugin page, the code editor background color is ‘black’ color. Why mine code editor background is white color?? (Is there a way to change the background color of your code editor?)

Thank you in advance.