Why I cant fix my screen

I was watching some movies on my phone then when I switch to an even bigger resolution. my phone just went on the craziest lag and then it just turn into a chocolate color and I can't open anything. the screen is completely chocolate so I cant see my apps. but if I scroll down I see my tools but when I press them for example the settings tool. it won't show me the settings. but when I try to call myself with my other phone it connected and it opened me to what's up but I can't see the chat only the display of who was calling me. I can press the restart and shut down button but it won't restart or shut down me. what is going on here?