Solo ads traffic works best with email capture funnels. Probably you should try to switch from WhatsApp to a more classic email + autoresponder followup where you slowly warm people who opted in and let them join your WhatsApp group
That page will not do well with solo ads. What you want is a simple lead capture page. Have a compelling headline and an opt-in form. Only ask for email and not name or phone number. If you set your list to single opt-in you will get more leads but they may not be as engaged. Personally, I use double opt-in as that ensures an interested and more "warmed up" lead. That's a matter of personal preference, however.
Thank you so much Christopher!