a few general remarks:
the landing page above-the-fold is just ugly, the color gradient is horrendous, and the top screenshot of a video is... blank. at first i tried to click the play button, but nothing happened. then i realized it's more of an abstract illustration of what you app does. makes sense, but a real video or animation would be even straight to the point. please, wow me!
what is mining? at first, i thought you've created a cryptocurrency. i see it's explained later down the page.
after login, the grammar page doesn't respect the light mode theme. more examples for grammar would be helpful. in fact, what i want is, extract relevant grammar from the CC of YouTube videos in Korean, and then link me to the EXACT TIMESTAMP, so i can hear it in actual use. i would pay for this.