帮忙看一下这句英语

depart from 是对的，be behind in 是拖欠、积压的意思，用这不太合适吧；然后silence是名词，如果是用来修饰behind you to watch,该用副词silently；还有不定式结构to do，所以watch不用加ing。

看你的意思，估计你是想说“我从来没有离开你，我一直在默默地关注你。”如果是这个意思，该这么说：
I have never left you. I've been watching you in the background silently.

如果不是这个意思，那。。。就改成“I never depart from you, and behind you silently to watch.”

没有

to watching you ?
to watch you 吧

I never depart you,and i will behind your silence to watch you

I never depart from you,and I will behind your silence to watch you.