WHAT TO DO

So, there’s this one client that’s about to drop the agency that I worked in. (I’ve only worked here for 6 weeks tops) at first i did not know that this client is about to drop our agency, and i made a few mistakes. The decission of dropping the agency was already made far before i work here. But still i made very little and very stupid mistakes that i myself can not believe (it’s a typo on a social media post..missed a letter) also i don’t even know what the past mistakes are, i’ve asked but no one seems to have th motivation to tell me. I have no excuse for this, and I have apologized, i also have improved and promise to myself that i won’t make any more mistakes. My first 4 weeks went well untill the client asked for many revisions in which created a chaos to my work. What more can I do to prevent the client from dropping my agency? Pls help.