We need youR* endorsement... You would mean "you, the other person", your would be "belonging to the other person", the endorsement comes from you, so it is your endorsement... hope it makes sense The rest sounds right to me, congratulations :)

I agree with Renan's corrections for the first two sentences. :) The 3rd sentence would read: This accident caused irreversible change in his life. (note "ble" vs "bly". I changed it to the adjective form.) The 4th: Her answer was irrevocably final, but he still hoped that she'd change her mind. (This was the best version I could come up with, based on my interpretation of the sentence.)