This is the end of the Gospel of John. Here the author, the Apostle John, gives a closing comment about himself and what he has written in this book. (See: [[rc://en/ta/man/translate/writing-endofstory]])
Here "testifies" means that he personally sees something. AT: "who has seen all these things" (See: [[rc://en/ta/man/translate/figs-explicit]])
# we know
Here "we" refers to those who trust in Jesus. AT: "we who trust in Jesus know" (See: [[rc://en/ta/man/translate/figs-explicit]])
# If each one were written down
You can translate this in an active form. AT: "If someone wrote down all of them" (See: [[rc://en/ta/man/translate/figs-activepassive]])
# even the world itself could not contain the books
John exaggerates to emphasize that Jesus did many more miracles than what people could write about in many books. (See: [[rc://en/ta/man/translate/figs-hyperbole]])
You can translate this in an active form. AT: "the books that people could write about what he did" (See: [[rc://en/ta/man/translate/figs-activepassive]])