Different size thumbnails on home and single pages

You can change variable $size value depending on what page is viewed.

$size = is_single() ? 'large' : 'thumbnail';

Code above will set $size to large, if is_single is true, else it would be thumbnail (or small as you said). Place it somewhere below shortcode attribute extract.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)