I cannot update or install any thing same problem in 18 as well

[Doctor loki]

First my internet was fine. I cannot install more like get the package from the internet like as installing docker for instance i get err while getting same of package form Internet

Problems seems like:
E: Failed to fetch http://np.archive.ubuntu.com/ubuntu/dists/focal-updates/main/binary-amd64/by-hash/SHA256/120b0d908c717cd34371791a19d0a0d56349d47f3e2c0cb55cba96e6fd928308 Hash Sum mismatch

E: Some index files failed to download. They have been ignored, or old ones used instead.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 5.8.0-43.49~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-43-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Sun Feb 21 00:27:48 2021
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed initrd=/casper/initrd quiet splash --- maybe-ubiquity
InstallationDate: Installed on 2021-02-17 (3 days ago)
InstallationMedia: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
SourcePackage: ubiquity
Symptom: installer
UpgradeStatus: No upgrade log present (probably fresh install)