First steps in Automatic Testing - Web Application

I will describe at the beginning what and why :) Well, in my company sometimes we have internal recruitment for different positions - we just pick up people from other departments who want to do something else. For some time, the web project has been extensively developed and tests so far are mostly manual and the issue of automatic testing is in its infancy (Is just one automatic tester). I would like to briefly shine a little before such internal recruitment, because I do not hide that I would like to take such an experience and I have a request for you - could you present me some interesting materials related to test automation? Issues of some load tests, security etc. - I do not hide, I want to show something more than testing typical functions. mainly I met Selenium and JUnit and a little bit JMeter - can you recommend something else? The project is based on C # + Angular and unfortunately I do not have access to the code. I personally can write something in Java or C #. I will be very pleased if you have some interesting sources of information about the automatic tests and it will not be a typical differences between automation and manual tests, or their pros and cons. I am more interested in specific tools, topics with interesting solutions - maybe some profiles on github with interesting automated testing projects, where you can see how someone approaches the subject.If anything else was important and I did not mention it, please write about it below.

Best Regards and have a nice evening! :)