This is the 5724th most frequent Russian word.
проблемой
"Проблемой" translates to "problem" in English.
The word 'проблемой' here is in instrumental case, used with the verb 'столкнулись' to signify interacting with the problem.
Мы столкнулись с серьёзной проблемой.
We encountered a serious problem.
In this sentence, 'проблемой' indicates the problem associated with the resolution process, being described as something that required time.
Решение данной проблемой заняло у нас несколько недель.
The resolution of this problem took us several weeks.
Here, 'проблемой' refers to the specific problem being addressed, in the instrumental case, as something the person helps with.