Forms and personal info

I have a website that I’ve built for a relationship orgainsation, and they have asked me to add a form to the site so that potential clients can fill in details, basically so that they have an understanding of what they will be confronted with/what the issues are.

Similar to this -

I’m thinking I’II be able to produce this in foundry (standing site was built in this), perhaps using forms and accordion. My 2 concerns are, how to get the first subsection to approve the content, before moving onto no 2, 3 etc. And not knowing anything about handling other peoples details, if they are filling in personal information, whats the best way for this to be sent. Is this form secure enough to then be emailed to them? I’m a bit of of my depth here, so any suggestions and pointers would be most welcome. Cheers Jon