I had problems like this when I was younger, too. When I started college the first time around, I'd have problems with "book report" assignments. When I was in high school, "book report" had a specific definition. It took years, a number of poor grades, and a move to another college to get it through my head that what they had meant was "critical review." I just couldn't get past my original definition of the words they were using. It occasionally still happens after all these years. I recently earned a very poor grade on an assignment because I just flat didn't understand what the professor wanted -- I thought I did, but it turns out he had a completely different idea in mind.
The best advice I can give is to talk to the professor and ask them to clarify the instructions. Point out the specific points that don't make sense to you so they can address it before you turn in the assignment. It may not be the magic bullet that fixes the issue entirely, but they absolutely can't help you with a problem they don't know you're having. Ask if a professor will let you redo something that has gone badly. If they find out that you simply didn't understand the assignment, they may let you rewrite it. Don't make this request very often, however. They may decide you're doing it on purpose in order to get more time to work on it. Also, don't be afraid to go to the professor while you are writing an assignment and ask if what you have done so far is acceptable or if it needs changes before you turn it in. If the prof is too busy, ask one of your classmates to look it over for you.