I’m sorry you had a bad experience on Fiverr. I feel like their cheerleader right now but I know there are some terrible sellers there … always have been. You can’t even always tell by the gig description because some sellers simply copy the description of someone else. But reviews do not lie. Hire someone with no fewer than 500 reviews, I would say, and all positive.
Obviously there is a big difference. I actually started with screenplays (with some mild success) partly due to hearing that as long as you have a good story, the grammatical errors won’t be a big deal. Well, that was not true. Maybe if a producer liked the story or I was already established but every contest I entered always came back with feedback about the grammatical errors. Even if I won or placed as a finalist, I always received critique on that. Very little is spelling error, it was more about structure, etc.