Language chance

I want to change the theme langauge into Dutch. I’ve tried a plugin called CodeStyling Localization but that doesn’t seem to work because of an error:

Error: The actual loaded translation content does not match the textdomain: aldehyde Expect, that any text you translate will not occure as long as the textdomain is mismatching!
This is a coding issue at the source files you try to translate, please contact the original Author and explain this mismatch.

Warning: The actual loaded translation content contains mixed textdomains and is not pure translateable within one textdomain.
It seems, that there is code contained extracted out of other plugins, themes or widgets and used by copy & paste inside some source files.
The affected unknown textdomains are:

Is there maybe any other easy way to get things translated? The only things i need is the 404page and the search-bar.

Thanks for your time!

greetings