Thank you for the advices. Maybe it would be good, if you could publish such recommendations in FAQs or Help-Site.
Like you mentioned in EX1 and EX2, the imprecise results are showing up, but however, if the most relevant are on the top, it is at least getting more useful.
Yes in the database there are a million keywords, the most of them are clutter and trash. Thousands of html-code and other useless words.
Maybe you can make the indexing of the database more precise, it think it would benefit performance and results hugely.