Enhance my website - UI and interactive functionality

I have a website that has an admin and registered users. The website is about helping our government school kids with English learning and supporting development of infrastructure at school. So the base site was developed using HTML/JavaScript/CSS file along with a friend of mine, but is has a lot of complicated code which makes it very difficult to change anything. Secondly I have added some interactive functionality by which a user can now register himself to become a donor, then he can donate using PayPal, and I as admin can administer these users. Now I may want to get away from PayPal because PayPal is now a standalone payment website for me, and I would like something that is inbuilt into my website and I can get the user information from the payment page as well, e.g. could be RazorPay but I am open to other options as well. I have also given access to the School Principal who can login and see all donations made by registered users and non-registered users. The Admin and School Principal (both are Admin roles with slightly different privileges) can also send emails to the donors from their login. The Admin also sends out the thank you email for the donation made along with a HTML receipt of the donation that has been made. Now the look and feel of this part of the functionality is not good and I need to make that very good. As of now I have separate pages, need to type the URL, for Admin and School Principal to login, however the registered user can login from the home page of the website - I would like to consolidate all logins via the home page and then depending on the user ID, the system should recognize if I am a registered user, or Admin or School Principal and give me the functionality accordingly. There are many such minor tweaks that need to be done. Also SSL needs to be done. There is some bootstrap functionality as well. The tech stack is as below: - To develop the website :- html/css/php/javascript - Front end APIs - Owl-Carousel/ boot-strap-Css - Database - mysql - Database management system - phpmyadmin The PayPal is completely off the site now and once the user gets to PayPal, I am not able to bring him seamlessly to the site. Plus, all the data that PayPal has I want at least the name and email address along with the payment coming to me in my database. I may also want to just get rid of PayPal and use something like a RazorPay which opens up as a Popup, you make the payment and then you are back to the site. And because I cannot do the above I had to create extra Admin functionality. I want to make it more automated if the payment and my site get integrated - for e.g. once the payment is made I would like my program to send a Thanks you email with the HTML receipt and I, as Admin, and the School Principal get a copy of this email. Some things to note that need to be done: - Vulnerability Scanning - Penetration Testing - Reporting - Source Code Reviewing - SSL Certificate Deployement - Mitigation other Security Loop Holes