[HELP] WordPress Conditional Forms in WordPress

I'd like a WordPress based website where I show a conditional form at the top of my homepage as done in this theme (A conditional search box form with an image as a background)

https://listify-demos.astoundify.com/classic/

Is there any plugin which can let me add such a form easily? Or, can someone share the basic code and the location where to add it in the theme.

Thanks for your inputs.