language redirect

hi everyone, theres some question I want to asking to all the joomla expert...

1. Why my website is redirecting to http://www.domain.com/en/?? theres always /en/ behind my domain so it ruin my navigation...
2. How do I turn off this thing??
3. when my SEF turn on, it coming back to the previous theme, but when I turn off the SEF..I can changed the theme..

thanks for all the help....sorry for my bad language..

Hi,

Can you please send me a PM to provide your backend access info to check configurations to help you better?

Thanks,