Why is việc used here?
Because "Learning Vietnamese" here is used as a noun. It becomes a "thing," a task, a chore.
vậy, đang học tiếng Việt cần sự siêng năng và sự kiên nhẫn say, đúng?
Việc hasn't been introduced as a grammar point. How is that supposed to be known?
Shouldn't it be "requires" instead of "needs"? "Needs" sounds kinda strange here
I totally agree.