First draft - is a rough sketch of your future piece of writing. Sometimes your first draft may become the final one due to it being rather satisfactory, but in most cases, it requires further work. A first draft is a way to elaborate on the main points of your essay stated in your outline, giving them a sample form.
Fill up - means to make something full, generally with a liquid. ... Since it cannot hold liquid, it is not appropriate to use “fill up”. The appropriate expression to use with a form is “fill in” or “fill out” (even though “in” and “out” are opposites, “fill in” and “fill out” both have the same meaning).
