From simple client/server applications to web development. How to switch in short terms

i am still a student but i now am an intern in student's lab. I have experience writing simple Java applications using Swing for front and having MySQL db. How can i simply switch to eg. Angular+Spring applications? It feels like they have absolutely different structure and "blocks" these applications built from. So if i recently had server parsing Strings and front just operating events, now i have to work on services, providers and a lot of other things i feel hard to understand. I will be really grateful for any help. The main reason forcing me to write such a question is absolute misunderstanding of such a simple thing as social networks authentication. I can't even understand should i make it on Angular side just sending info to Spring server or using Spring social to auth having just a couple of buttons at front and receiving token there.