[TYPO3-ttnews] tt_news is so slow on the backend

[Ahmed Moosavi]

Hello ,
I've imported three fields of a Joomla database to the typo3 tt_news 
tables through mysql queries . The imported record count is about 20'000 
but when I try to list these new tt_news records on the typo3 backend I 
should stay for about 15 seconds for 100 items of these . Can anyone 
help me what can be the problem ?

Best Regards
Ahmed