Joomla is a powerful tool. It can make a website much easier to manage, especially large websites, but it may also take a little bit of learning. Not everyone can expect to just pop a site up and know what to do, just like you can't just pop someone behind the wheel of a truck and expect them to drive it well.
Stick to the Basics First in Joomla
If you are new to Joomla, stick with the basics first. How to add/edit content, and add/edit menus. Then maybe take a look at Components and Modules. Do not add a bunch of extensions in while you are learning the basics. Keep it Simple. Add/Edit. Only when you are comfortable with the simple should you look to learn more. Below are a few helpful sites with tutorials, themes, and extensions:
Read more: Joomla Help