Greasy Fork is available in English.
Press Esc twice to toggle the menu,and save the setting
I don't think this script is the root cause.
Try disabling this script from the tampermonkey icon,then refresh, the game will run without this script excuting. If the game still says modified game client, it has nothing to do with this script.
It's possible one of your extension causing the problem,disabling them one by one and test.
After using it for few days it is saying You are using a modified game client.
How to bypass that?