Line 2: you are talking about interactive subtitles, the 's' at the end of subtitle makes it plural so you are talking about more than one of them. When you have plural nouns like this you don't need to use indefinite articles (a or an). Line 3: again you are referring to the subtitleS, so you want your subject to be 'they' not 'it' because there are many subtitles. Line 6: I'd like to suggest you use my system for your videos. You don't need that 'to' after 'you'.