Stackoverflow is for asking specific questions about specific problems in specific code. Within 1 post we cannot and will not review your entire repo in relation to a whole series of broad points. You
may get a better experience on the Code Review site I linked to, but
please carefully review their guidance
before posting. Take the
tour and read
How to Ask to improve your experience here. I've already explained why just posting a link to your site and repo is not accepted here. External links can change or die over time, and your working frontend is irrelevant to analysing the backend code. —
ADyson 52 secs ago