"If you studied well..." Yes. Although I don't think "well" is the most common adverb to describe the quality of studying. Native speakers will hopefully tell us.
"Good" in "good English" modifies "English". It's an adjective modifying a noun. "Well" in "studied well" modifies "studied". It's an adverb modifying a verb.
As for the past progressive question, you seem to be asking an infinite number of questions regarding English tenses without trying to apply logic first. You certainly know what difference there is between progressive and simple tenses. What is your opinion on this?
"If you were working hard (rather than just pretending, which is what I suspect) in the last semester (on those occasions I saw you with your head in a book), you are going to understand everything the professor will be talking about (in his lecture next week)."I don't know if it's possible in your example. If you can come up with a good context, then it's possible. If there's no such context, it's impossible.