searchform.php is not working

Hey, I use Local and everything worked just fine till now. I am using searchbar inside my sidebar and it seems to work fine, but when I want to change it via searchform.php it just doesnt do anything. I am not able to change even a placeholders… Any known errors with local or help? I tried this tutorial: https://www.youtube.com/watch?v=pLwephEKF5Q&list=PL0-e1OMq5RP4LVmPKRljF5vAU3-Jx3yWQ&index=20