翻译及结构分析let's say you are trying to learn some new and rather

让我们来假设,（有这样一个场景）,你想借用一沓卡片来学习一些新的、有相当难度的英语词汇.
全句是let's do sth（让我们一起干某事）这一形式的祈使句,say是谓语,这里意思不是说,应该理解为“假设、假定、想象”.you are trying to learn some new and rather difficult English vocabulary using a stack of cards.是宾语从句.从句中主语you,谓语try,to learn some new and rather difficult English vocabulary 是不定式作宾语.using a stack of cards是现在分词作方式状语修饰动词learn

纠正一楼一个错误，上文中的some不是一些的意思（从vocabulary 未加复数就可以看出）
这里的some是“某个”的意思，如：
1.
She won a competition in some newspaper or other. 她参加某报纸举办的比赛获胜。
2，
Some man at the door is asking to see you...