Hello! 

The sentences look good, but here are a few grammar corrections for them: 

1. "The needs of ethnic groups for both diversity and harmonization also exist off-campus. I thus connected myself to the need for local diversity as a member of the campus..."
2. Together, we can develop ideas and provide programs towards building mutually beneficial relationships between faculty, staff, students, and the local community." 
3. Besides my involvement in diversity for ethnic communities both on and off-campus..." 
4. "I have participated in this annual event for four years, which helps local poor households and supports mission trips." 

I hope this helps! Let me know if you need anything else, and please don't forget to rate my service! Thanks. =)