In your presence his mouth is all sweetness may be rendered “When he’s with you, he talks nicely [or, sweetly]” (similarly Good News Translation). The hypocrite has nothing but nice things to say in your presence.

And he admires your words: Actually, he says that he admires your words. He doesn’t mean it, but “He compliments you on every word you say” (Good News Translation). We could also say “He says he agrees with every word you say.”

But later he will twist his speech is literally “but later he will distort his mouth.” This means that when he is not In your presence he will no longer say such nice things. He will say bad things instead. Good News Translation “But behind your back it’s a different story” is well done, but is too idiomatic to serve as a model. New English Bible is similar with “but later he will change his tune.” A possible model is “But later he will say only bad things about you.”

And with your own words he will give offense: Good News Translation again gives the meaning here nicely, but idiomatically. This line means that he will use your words (which he has complimented you on) against you in some way. He will report what you have said in some way that will result in harm to you.

An alternative model for this verse is:

• When he’s with you, he talks nicely [or, sweetly], and says he agrees with every word you say. But later [or, behind your back] he will say only bad things about you, and use your words against you in some way.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Sirach. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here.