i need help on how to do a complete university portal website where exams can be taken online , courses registered online and online payment etc
2. do u think its better done with a cms like wordpress or joomla if yes how secured is it?
for any assistance call me or sms me 08063427286, ughegheehiosu@gmail.com

With wordpress and Joomla? NO!! You need a more advanced framework........

you can still use WordPress or joomla but you will be writing the backend for some specific features, and you need to be really good in php too

Yes I thinks it's better done with with Joomla! or Wordpres.
Joomla! or Wordpres are sophisticated frameworks with wide array of developers/community, meaning you could easily get or third-party extension anytime. The security of those CMS all depends on you, it's more secure if you believe and work harder, their security teams are doing great to ensure maximum security always. Mind you, no application is secured if you don't update your security vulnerabilities...