The font size in the select fields is quite friendly towards really really short sighted people, but maybe 100px-200px is a bit much, it also kind of ruins the layout
(I think you mixed up font-size and padding a couple of times)
Also, instead of this:
margin: 0px 400px 0px 410px;, it’s much better to use
margin:0 auto. Imagine what happens on a smartphone with 360px width, and you give an element a margin-left of 400px…
You can also drastically increase responsiveness if you give your
<form> a max-width of maybe 500px, center it with
margin:0 auto, and all the inputs inside get a width of
100% (or 90%) and again
margin:0 auto to center them.
Now for the form elements, it’s always a good idea with radio buttons and checkboxes to nest the input inside the label, or to use the
for attribute, either this:
<label for="my-checkbox">label text</label>
<input id="my-checkbox" type="checkbox">
That way, you can click on the label and it’ll check the checkbox. Right now, you have to exactly hit the tiny box to check/uncheck a box.
You also have some HTML errors (
<input type="birthday"> is not a valid input type, for example). You can run your code through a validator like this: https://validator.w3.org/
Last issue - you use a lot of
<br> tags for spacing between the inputs. That should rather be done with margin-bottom.
But on the plus side, that’s a good clean design, and the text is readable even on the image background.