It is generally agreed that all the people is a reference to the Jewish people.

The witnesses that God had already chosen may be rendered as “we are the ones that God had already chosen to be witnesses of him” (or “these events”).

We ate and drank with him is doubtless a reference to Luke 24.13 ff., 36 ff.. “Eating and drinking” is, of course, a reference simply to “having a meal with.” In some languages both activities are specified, while in other languages a general term groups both activities together.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on The Acts of the Apostles. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .