cannot upgrade from 14.04 to 16.04

[Nicholas]

if I try to use the software updater or the terminal to upgrade, I get this message:
Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

If i search for broken packages, I get 700 entries. What should I do?

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.9
ProcVersionSignature: Ubuntu 3.16.0-77.99~14.04.1-generic 3.16.7-ckt27
Uname: Linux 3.16.0-77-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.23
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Wed Jan 11 12:08:02 2017
InstallationDate: Installed on 2015-07-30 (531 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2017-01-11 (0 days ago)
mtime.conffile..etc.update.manager.release.upgrades: 2017-01-11T11:10:28.610782