Securtity Assesment/Audit of Online Portal

We have designed a web portal which helps businesses manage gift cards so customers can easily purchase gift cards from them and they can redeem gift cards through the portal, view reports or gift card history etc...

I am looking for someone who can complete a security assessment of the portal and advise if there are any vulnerabilities present and advise on any additional precautions we should take. As the portal has recently been designed we have taken security seriously from the outset and we have followed best practice. The portal is currently hosted on Microsoft Azure and we are using Google Firebase for the databases.