Hi please I need help! I bought an iMac from eBay and it’s in a Poland language from the restoration and I’m trying to restore to English but I couldn’t and it’s the beginning of the screen in the setup.
Provide more information about your Mac. What machine configuration is it? What OS did the seller state was installed on it? Need to figure out how old this iMac is and what OS it is capable of running and currently running.
Did you try the steps listed in my link? Which ones?
Here's Apples page in reinstalling the OS using recovery. You can install an OS using a bootable USB drive but that requires that you have a Mac running that you can use to create it (obviously this one is not usable since it's not in a language you understand).
You can use macOS Recovery, your computer's built-in recovery system, to reinstall the Mac operating system. Reinstalling macOS doesn't remove your personal data.