Figure out: to think about sb/sth until you understand them/it 弄懂;弄清楚;弄明白
We've never been able to figure her out.
我们一直没能看透她。
I can't figure out how to do this.
我弄不懂怎样做这件事。
get the hang of sth: to learn how to do or to use sth; to understand sth 掌握…的要领;了解…的用法;找到了诀窍
It's not difficult once you get the hang of it.
你掌握了要领就不难了.