Hello,

I have this online shop that I am trying to configure:

www.advance-web-studio.com/bestshop/
and
www.advance-web-studio.com/bestshop/index.php

How to make the first one direct to the second one. The result is different. I expect the second one appears not the first one.

Can anyone help me out?

It's because there's also an index.html in that 'bestshop' directory and that's the one that gets loaded when accessing www.advance-web-studio.com/bestshop/
http://www.advance-web-studio.com/bestshop/index.html
As far as I know loads Apache by default an index.html before an index.php unless you tell otherwise (a diffrent order) in a .htaccess file.

If you want to load the index.php you can also remove the index.html or rename it to something else if you want to keep it,

If you are focusing on seo also then I suggest you check if the pages are duplicated. If you want to tell google what is the main page
Add this code to your index.
<Link href = "www.yoursite.com" rel = "canonical" /> ( Place the main page )

Site to check duplicate content: http://www.siteliner.com/