Even though I was a noob Translator in the past, I still check the Subject before any Verb.
@Translator: you should check who is speaking because Japanese tend not to have a Subject.
Mistakes:
Page 3:
the Duke-Bro said back to the Butler "Cut/Remove the Young Part in the Young Master" (The Butler has always called the Duke-bro so since he was young)
And the Butler answers as you translate.
Page 4:
The Duke-bro asks "With so many farmlands, why can't THEY (not we) develop?"
Page 8:
The Duke-bro says "How sly of her (Grand Duchess)" (Meaning the secret assassination order)
The Grand Duchess (Not Mistress) gave the "assassin (not the Butler so you can't use "me")" the order
Page 9:
And that's why page 9 will be translated a little differently.
Even after the Duke and Grand Duchess died, the "assassin" (not I think you) still followed the order.
"I was also Negligent" meaning: he didn't check all the servants so he missed the assassin.
Page 18:
Ekaterina said "While mother was alive, she wanted me to marry the prince and become the empress so that even the Grandmother must bow down to them"
Next bubble
Ekaterina said "I don't want to marry into the imperial family where grandmother grew up (whom both siblings hate)"