Joomla is the next big name in CMS after WordPress. A lot of users trust Joomla and its addons. They have a very vibrant and active ecosystem and enough community resources for help. A lot of forums support when you need help with Joomla. Considering that is around since a few years and widely used, we can assume that Joomla is easy to use and a safe CMS.
https://community.joomla.org/joomla-training.html
The link above will walk you through
- Beginning in Joomla
- How to maintain a Joomla website ?
- How to keep your Joomla websites safe ?
- Build Multilingual sites with Joomla
- Joomla and associated SEO
I hope you experience with Joomla is good one.