The person speaking is not specified. The "voice" was probably God, although it could possibly have been an angel from God. See how you translated "a voice" in [Acts 10:13](../10/13.md). (See: [[rc://en/ta/man/translate/figs-synecdoche]])
Apparently the animals in the sheet were animals which the Jewish law in the Old Testament forbade the Jews to eat. This can be said in a positive way. AT: "I have eaten only meat from holy and clean animals" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-doublenegatives]])
It is not likely that everything was repeated three times. This probably means that "What God has cleansed, do not call it defiled" was repeated three times. However, it may be best to simply say "This happened three times" instead of trying to explain in detail. See how you translated "This happened three times" in [Acts 10:16](../10/13.md).