Recently, we launched separate URL site m.example.com for mobile users, but we did a mistake that we don't have the same page on mobile which we have for desktop version. I mean we have less pages on m.example.com website as compare to www.example.com.
Google already started to index our mobile page, and thus keywords for desktop are continue to disappear. To recover from this problem we thought to put rel = alternate and rel= canonical but as I said we don't have all pages on mobile, even some products are not available for mobile so we didn't have these pages for mobile.
Then I thought to make responsive version, but it can take too much time. I hope I will get some good solutions by posting the problem here!