I've done a lot of OPIC private tutoring.
Keep in mind that all four areas of English (listening, reading, writing and speaking) are different subjects. 'English conversation', the difficulty of speaking is actually the lowest among the four areas.
Because Koreans are weak in speaking due to the nature of education they have received since school days, there are many people who struggle in exams such as OPIC.
Based on my extracurricular experience, I developed an application that allows you to easily acquire IH by following the curriculum for a period of two weeks.