How do I terminate a tutoring center contract?

Hello! I am currently struggling with a contract issue with my academy. The current contract is from June 2025 to June 2026, and I signed an extension contract for the period from June 2026 to February 2027 in February 2026. However, due to a recent incident, I am considering terminating the original contract and withdrawing the extension. Having just switched to an F-2-7 visa, I informed the academy's headquarters that I would not be proceeding with the next contract. However, they mentioned that I need to submit an internal resignation letter to receive my severance pay on time. I emphasized that this is not a resignation but rather a completion of the contract and a withdrawal of the extension. After several discussions, they sent me a resignation letter template and accepted some of my requests, but I am concerned about the lengthy Non-Disclosure Agreement (NDA) included. This NDA requires the return of materials, deletion of audio files and evidence, and also makes me waive my right to show evidence to a lawyer in case of future civil litigation. What should I do in this situation? I would like to hear your opinions.