请帮忙翻译并分析下句子成份!

I was moving forward over a slope
我正向一个斜坡行去that 指前面一句话 后面接从句seemed safe 看起来很安全 when 当...时 时间状语从句 suddenly whitout warning 没有任何警告 作状语 my world dropped out from under my skis.当我突然从脚底下的滑雪板跌落

这句意思

当我突然从滑雪板上跌落的时候我正向一个斜坡滑去

i was moving forward over (a slope)主句一
a slope (that) seemed safe定语从句
when suddenly (whitout warning)
my world dropped out from under my skis 时间状语.

主句一（+ 定语从句） + 时间状语

当我向一个看起来安全的斜坡滑去时，毫无征兆的摔了个仰面朝天。

这个句子最主要的结构
I was .... when ....

所以主句是I was moving forward over a slope 。

那应该翻译为：
当我在没有警戒的情况下突然从滑板跌倒时，我正在滑向一个斜坡。

这样就强调主句的进行时态

i was moving forward over (a slope)主句一
a slope (that) seemed safe定语从句
when suddenly (whitout warning)
my world dropped out from under my skis 时间状语.