Dear Swara K,
Hello! Welcome to the Microsoft Community.
It sounds like you are using a Korean keyboard and want to know how to quickly switch between "English input mode" and "Korean input mode".
You can do this by pressing the "right Alt" key on your keyboard. The "Alt" to the right of the "spacebar".
Under my testing, this switch may not switch in some cases, such as focusing on web content. But when I am typing, or focusing on the desktop, etc. It can definitely switch quickly.
I hope the above content helps you.
Best wishes
Pyke.D | Microsoft Community Support Specialist