In some languages You have seen well is not a natural response. See, for example, “You are right” (Good News Translation) and “You have seen correctly” (New International Version).

For is a simple transition word here, and can be dropped if it is not natural.

I am watching over my word to perform it is translated “I am watching to see that my words come true” by Good News Translation. Die Bibel im heutigen Deutsch has “I am watching to see that what I said to you happens.”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on Jeremiah. (UBS Helps for Translators). New York: UBS, 2003. For this and other handbooks for translators see here .