1. mark my words 就是告诉别人某事将来肯定会发生时的用语，意思是（你）记住我的话！

He'll cause trouble - you mark my words!

他会惹麻烦的——你记住我的话！

2. slip away 主要有这两个意思——

<1>秘密地离开

It's a good time for you to slip away.

正是你溜之大吉的好时机。

​<2>（时间）很快地过去

Time was slipping away and she had to make a decision soon.

时间飞逝，她得赶快下决定。