Hiding the preflight request that shows my data in network tab browser

I'm developing a website with Strapi(backend) and Next.js(frontend). I'm new to this. I'm currently trying to improve the security and noticed that my data was visible on the network tab so I decided to filter the data sent. It still isn't enough. The website is a subscrition business model, anyone with a monthly subcription could steal the data they are allowed to see in 3 clicks and never come back the next month.

Is there any solutions to improve the security ?

Here is my network tab with my filtered data.

Thank you