The version of mySQL you are trying to install will not run on Ubuntu 16.04, as it is very old, and its dependencies are also older and outdated. If possible, look for a newer version of the software that isn't running on newer mySQL versions, or an alternate software that is being updated.

It is highly not advisable to run any framework/CMS/application that has not been updated to support a later version of MySQL/MariaDB. That may also mean that the application itself has not been updated at all, and consequently, it may be vulnerable to exploits. Either use a newer version of the framework, or switch to a newer, frequently maintained and widely supported one.