Ask HN: Asp.net Best Practices and Optimization Resources?

Hey good day everyone, I've recently been made the de facto 'lead' developer at the company I work (currently the only full-time dev due to reasons) and the solution I am working on is an ASP.Net application. Its about 6 years old at this point, and while the original devs (including the higher ups who still work on it from time to time) put in lot of future proofing and who actually implemented performance and good practices, the amount of devs who have come and gone has made the solution not the best. I've been looking for best practices and optimization considerations, and if possible if anyone has any recommendations I would really appreciate it.

Also I've been trying to hook it into GitLab's CI/CD which has also been quite the experience. (Not good lol)

Thanks in advance.