Common errors in development (#25)

start with help for common errors in development

Author: chmst

docs/common-errors/index.md

@@ -4,7 +4,29 @@ sidebar_position: 9
 
 Common Errors
 =============
-Some frequently asked questions on Error messages and how to resolve them
+Some frequently asked questions on Error messages and how to resolve them. 
+
+As a developer you somtimes will be stuck in your code. 
+If it happens to you, also have a look on https://joomla.stackexchange.com/ - a huge collection of valuable knowledge. 
+Here we collect some frequently aske questions. 
+
+Class [..] not found
+--------------------
+
+You need to understand the namespace concept as described in sction General Concepts (work in progress)
+Then check:
+- Is the namespace defined in your manifest file? 
+- Has every class in your extension the correct namespace?
+- Is every filename correct and matches the namespace? 
+
+Examples: 
+Code: use FooNamespace\Component\Foos\Administrator\Extension\FooComponent
+
+But the filename is src/Extension/FoosComponent.php 
+
+
+
+
 :::caution TODO
 
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