Welcome to NinjaForge and thanks for your kind words.
First, make sure when you have enabled SEF in Joomla that you have renamed the htaccess.txt file to .htaccess (dot htaccess).
Also try to disable the Add Suffix to URL option if enabled.
If this doesn't help, please provide a link to the page in question so we can have a look at your issue.
You may also post your system info which gives us additional info on your server specs.
To do so from the menubar in the backend go to Help > System Info > System Info (tab) > Copy and paste the provided info.
Second, Ninja RSS only does retrieve content from articles and can't retrieve info within menu items.
Globally, RSS content only contains article content from given sections/categories.
I hope this helps.
Let us know how it goes.