Hi @carolvieirav and welcome to the LE community forum 
If you are to provide access to a database to anyone directly over the Internet, HTTPS is a requirement; But getting a globally trusted CA certificate for that has its' own requirements.
That's not going to work.
You really should read up on how to enable HTTPS.
This is a forum to help people when they have a problem implementing a solution.
You are looking for a solution - to which there are an infinite amount of possibilities.
https://community.letsencrypt.org/t/authorization-result-in/165852/2