Language learning strategy and tactics are different for different people in various stages of their learning journeys, so it’s impossible to give you personalized advice without a full understanding of your current situation. That said, having read your post and looked over your profile, my recommendation is that you stop using subtitles in your native language — immediately. If you can’t understand the English subtitles, then you can occasionally turn them on briefly, or else find material that is actually comprehensible. Also, if you are serious about speaking and listening (rather than just reading and writing), you should stop using any subtitles ASAP. Your writing looks to be coming along nicely, but if you’re like most Koreans, you may have poor pronunciation. Since the way we speak is the way we listen, poor pronunciation would make it difficult for you to understand native speakers even when you know every word and all the grammar.

You can watch a film with 2 subtitles 😍 Install LLN (Language Learning with Netflix) on your browser. Then put the targeted language as the bigger subtitles and your native language as the smaller subtitles.

Well I think watching with Korean subtitles is fine. It's better for you to understand if it's your first time to watch the video. You can then switch to English subtitles when you watch it for the second or even third time.