What related technology to choose when creating the described web project?

Question

PHP

Hello, I would like to ask you what is the best thing to do when typing the following data:

The task is to create a web service for organizing competitions, php, js are indicated from the technologies. My question is, how can I implement this service as a site for multiple users to use at the same time and how to ensure the safety / security of the data (as for example when accessing the database)?
I was thinking of wordpress as a framework that can help me with this.
The idea is this: we create a page on wordpress, I write its source code myself (input fields, data processing logic, handling this data in the database), and with the help of wordpress, the security of accessing the database is ensured; and the same multiuser part.
But in wordpress, I'm not strong yet, so of course I can't know whether it will be possible to implement everything in this way or not.

Therefore, I would like to ask knowledgeable people - what is the best way to go down in this situation, what is the best choice, where to move? Perhaps it would be possible to implement everything according to the scheme voiced above, but with a different technology? Or would you do it differently?

I'm afraid there may not be enough time on Asp.net; and the project after the delivery does not need support, because it is more likely to "hand over and forget."
Thank you.