en_tn_condensed/ecc/07/23.md

All this have I proven

here the word "this" refers to all of the things the author has written about. Alternate translation: "All this that I have already written about have I proven" (See: rc://en/ta/man/jit/figs-explicit)

it was more than I could be

"it was beyond my ability to understand" or "but I was not able to do it"