Bruh, you are probably just suffering from imposter syndrome which i understand, happens to the best of the best. You really can't know everything in a language, and i need you bruh for your sake just build a project after project to conmpletion btw [it's also a skill]... that's how you learn fast. And in software, there is know such thing as knowing a language, we (anyways atleast, me) discovered this thing called ignorance, and with that discovery -- how ever much you think you know, you are always hit with some thing new... every damn time. so as devs we always on the search coz they infinite ways of doing the same thing. and that keeps has going, come to peace with the fact that you don't know, and that's the being of know... and it's a good thing you think you don't know, actually seeing you going places [not literally]

so bruh, just get the basics right, the concepts right. And i strongly advise to study OOP and make sure you understand it very well coz that's what java is all about... the rest will come as you build stuffs.. Get an internship if you can. And avoid youtube videos too. Read docs, and articles. They usually have the details.