You can learn anything given enough time. The main thing is not to try to learn everything at once - focus one or just a couple of things at a time; learn them well; use them regularly so you retain the information. Build up your personal library of notes and code samples so you can pick things up again later.
Also be clear on the difference between concepts, methodologies and languages; so you can work out how you learn them most effectively.
In terms of "mastering" multiple stacks - the wider you spread your attention, the less you can deep dive into any specific thing. Earlier in your career it's normal to learn a wide range of things, over time you'll find the things you really enjoy and naturally want to dive in deep and truly master. Or maybe you'll become a really well-rounded generalist. There is no "right" way, do what you enjoy; keeping an eye on what will keep you gainfully employed ;)