You've previewed the topics that take you from Java student to Java developer: file I/O, packages, enums, records, sealed classes, lambdas, streams, Optional, generics, multithreading, build tools, testing, and Spring Boot.
None of these topics require starting over. Each one plugs into the OOP and collections knowledge you already have. Pick the area that matches your goal, build a project around it, and practice on a coding platform to sharpen your problem-solving skills.