Integrate Mailchimp (and Paypal button) into Wordpress page

I need a wordpress developer to help me integrate a mailchimp form into my wordpress page. I currently have a version of this but it is not working correctly.
Website page: https://www.gordonrusselldesignmuseum.org/friends-sign-up/
The 'Subscribe' button should link to Paypal, take payment, then record the record in my Mailchimp account.
Also there is a MariaDB (Wordpress) SQL table that is used to record these same onscreen form details.
The Wordpress page makes reference to:
[paypal-mailchimp-form]
The fix needs to establish the connection to Paypal, Mailchimp and write the row into the SQL table. Most of this must be available as it used to work a year ago - but now no longer works.

From a user perspective of the website offers a subscription to Friends of the Museum - which costs either 12.50 or 15. Hence the form allows us to take their details and payment.

Once I get this working there will be a second project to smarten up the subscription page, add other payment methods and also allow a notification when we have new subscribers.