Customisation of existing website database application

General information for the business: Custom Database Reconfiguration
Database management system (DBMS): MySQL
Description of requirements/functionality: We require some changes to our existing website database:

We are looking for an experienced web database developer. The database is built and hosted on our server, stored on MySQL..

We are looking at adding the following features:

1. Invoice system that sends an invoice to the customer and allows them to pay via the already integrated PayPal pro.

2. We need to integrate an API, very basic, just sends the persons details to an online identity verification system and it pings back a result that is shown in the database.

3. We would like to integrate Dropbox to store files for clients within the database, so this will mean wkring with the dropbox API.

4. We need to link to Companies House (UK) so we can pull information from a company and then populate the database.

5. Improvements needed on the "tasking system" we already have.

6. Improvements on the messaging within the database.

7. We need a to be able to send an email to the database and for the database to be able to store it under the relevant clients account. So in theory we need a custom created email for each client in the database that allows us to send an email to the clients account and for it to store the attachment in the database.

8. Improvement of clients login, they should be able to see and download the finance / invoice history

9. Improvements on layout of the current design.
Extra notes: