I am a native English speaker from the U.S., now living in Germany completing my Master's Studies. My writing abilities were lauded throughout my college career and led me to eventually win a scholarship to study in Germany. Currently I am a writing consultant for my city's Hochschule and work with students from varied backgrounds to help them achieve the writing style then envision.
I can understand the frustration of having one's writing not be quite up to one's standards or expectations, and I would happily work with you to try to understand what your vision is and make edits accordingly.