RewriteEngine - with .htaccess ( How to transfer all requests to one file? ) HELP!

I really have no idea how to actually do this,
Could someone please tell me how could I do this thing with .htaccess
, I wanted to re-make my website but I have 95% of traffic comming from searchengines to more then 2000 different pages but if I would do this I would lose almost all my traffic!
So anyone could tell me how can I get this that, all requests for files what is on my domain - for example domain.com/se/43423/34qwdasd.php redirects to one main file at domain.com/index.php ? |but not only one specific directory or file but ALL Files what is on that domain!

Thank u very much!

That's easy, I do this when I perform site maintenance:

Thanks, you really are lifesaver!