Greek language problem

Hi,
am trying to put greek language in this site and the site collapse. Am sending a screenshot. I have install all language packs for joomla and virtue mart and when i enable greek language in site i believe virtuemart crashing.

After language pack installation you usually have to go to Extension manager, 'Database' tab and slick on button to repair database (it will be available if repair is needed)

I have done that but nothing happened.

Try to create tables manually editing database by copying tables ending in _en_gb to _el_gr

This is the only way? I dont know how to do that

I renamed the tables from en_gb to el_gr and the problem solved. Now i have another issue. Am taking the error
Missing Flag el-GR for language el-GR.
Go to Extensions > Language Manager > Content, and check the parameter Image Prefix for this language.

I have checked the language parameters and are correct.
Is it important?