I am worried I will not understand. Can I follow a makeup lesson in Korea?

Yes. The class at RihaKim Makeup is taught in English, slowly enough that you do the step yourself before the next one starts. The relief is realizing you are not nodding along to a language you cannot use on your own face.

Fear of the language is why people skip the lesson

Travelers assume a beauty class in Korea will move too fast, in Korean, and leave them smiling and lost. A private English lesson removes that. You hear the reason for the step, then you do it, then you are corrected.

What fluency you actually need

You do not need perfect English or any Korean. You need to be willing to try the step while someone watches. That is the whole barrier. Once it drops, the reward is a look you understand, not a look that was done to you.