2 Things:
If you're gonna say something like that their translation is "unfaithful to the authors intention" you gotta provide some examples of such. Same goes for the grammatical and translation errors.
Secondly, and arguably more importantly, you can't be this slow releasing chapters when there's someone else willing to do it at a much faster pace with comparable quality.
Idk what your previous situation was but maybe learning to work together would be ideal since it seems like you're doing everything here alone and so is he. Split the work between translating, cleaning and whatnot.