"हम खाना खाते हैं।"
अनुवाद:We eat food.
Y only used lunch? We can say meal only. They did not mention dopahar ka khana, raat ka khana!!
Because this sentence is include in present tense and in the present tense helping verb is s/es for simple sentence and only with first person (he, she, it, or name ) we put there s/es in this sentence we is a plural pronoun