I'm not a website but here's two suggestions.
1. Start with one sentence. Expand that one sentence to a paragraph starting with premise and main character in the first sentence. Next three sentences cover what goes wrong in the three acts, end with a final sentence being the resolve. Then expand those sentences into a paragraph each.
2. Write out a bullet list of your main points and characters and obstacles and goals. Trim it down, organize it, order it, then expand out those points. It makes for a lot cleaner and focused first draft.