This looks nice I'd just address a few things. First thing is I would set font-size in rem units instead of pixels, this helps both accessibility and responsiveness. Second thing is on your paragraph text, instead of using <br> tags for every line-break you could set the max-width of the paragraph to something like 50ch. This is a really common strategy to make paragraphs more readable and easier on the eyes. Another thing is giving paragraphs line-height of around 1.5 (unitless). One more thing I'd do it clear the form when the submit button is pressed. Currently when you press the button the fields don't have their values cleared.
Other than that I'd say it looks good, for places to improve I suggest using rem for font-sizes and other measurements. Another thing is try to size things implicitly by setting a max/min height/width and letting the inner content size the box, instead of explicitly setting widths and heights. Good job overall it looks really nice!