Interested in Language
1) Can you please make a recommendation on/about what to order?
2) One of server's duty is to make food recommendation to customer.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
Thanks for pointing out the mistake I've made and correcting them for me.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.