Custom Form field with validation

Hi

I’m creating a form i.e Ask us anything

it’s a simple form but need some validation too.
Placeholder says Ask us any question then submit button, then popup opens which output the input character submitted (in ask us any question) and then they have to submit thr email address to complete the process

I know some contact form like ninja forms do validation process for logged in members etc but don’t know how to make exact similar process 2 step submission

simple javascript can also solve this plblm but i want to know wordpress process

thanks