I'd start by losing the 'respected management' bit and substituting some actual names (and possibly their associated job titles). So my version would be along these lines:
"To: Sarah Smith (Head of Media Management)
Copied to: Jane Doe (Human Resources Manager), Phil Parker (Social Media Team Leader), Steve Tricker (Web Development Team).
I have been creating content for the company's social media pages for the past four months. Although I have always sought to produce work that is both accurate and innovative, my efforts have been hindered by my difficulties in working in English which, regrettably, has resulted in me making many errors.
I feel that it would be better, both for the company and for myself, if I were to be relieved of the task of creating social media pages and reassigned to a different role within the company, where I could make better use of my skills.
I hope that this suggestion will meet with your approval and I look forward to hearing from you.
Regards"