Filter custom post types in archive

I want to filter my custom posts (pump) with a custom filter form on it’s archive page (archive-pump.php).

So, I wrote the form markup:

And I have this to output my custom posts:

When I open my page (localhost/project/pumps) it looks fine.
But when I submit my form I’m getting an 404 page.

I maybe need an seperate query to fetch all the $_GET data. But I’m not getting to the step because of the 404 error.

What am I doing wrong? Thank you!