Please help me on this error:
E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/main/source/by-hash/SHA256/d9e8a5b1e94cbdf17ae488b506e45ba117c6e9778b1af2a97789d3a2983f888d Hash Sum mismatch
This site is for the co-ordination of the Ubuntu project(s), and not support.
For Ubuntu Support options, please have a look at https://community.ubuntu.com/t/finding-help/712