Bugs and Issues
If your server has a support page, you should report any bugs/issues you encounter there first. Reporting to your support page before reporting to the developers makes their job easier, as they don't have to deal with bug reports that might not have anything to do with them. Reducing the workload in this way helps us get new features faster. You can also contact the friendica support forum and report your problem there. Bugs are rarely limited to one person, and the chances are somebody from another node has encountered the problem too, and will be able to help you.
If you're a technical user, or your site doesn't have a support page, you'll need to use the Bug Tracker. This is also used for issues with addons. Please perform a search to see if there's already an open bug that matches yours before submitting anything.
Try to provide as much information as you can about the bug, including the full text of any error messages or notices, and any steps required to replicate the problem in as much detail as possible. It's generally better to provide too much information than not enough.
See this article to learn more about submitting good bug reports. The better your bug report, the more likely we are to be able to actually fix it.
And last but not least: It is better to report an issue you encountered even if you can't write the perfect bug report!