"What did you eat?"
Translation:तुमने क्या खाया?
The past tense is a little strange in Hindi. When using a transitive verb, you would use the particle ने following the subject. A transitive verb is any verb that can be done to something. For example, you eat a vegetable or draw a picture. Meanwhile, intransitive verbs cannot be "done" to a noun. For example, sleep, appear, or look would all be intransitive verbs.
This sentence is using the transitive verb खाना (to eat). Because we are putting a transitive verb into the past tense, you would have to add the particle ने after the subject of the sentence, resulting in तुमने. Next, the transitive verb will always take the gender of the noun it is acting on. For example, if we were talking about an apple, the sentence would be "तुमने सेब खाया." However, if you were talking about a vegetable, the sentence would be "तुमने सब्ज़ी खाई."
Past tense of खाना
Because we are not talking about something specific being eaten, the past tense of खाना would default to the masculine खाया.
Put क्या as the first word in the sentence to make a yes or no question. For example: "Did you eat?" would be "क्या तुमने खाया" "Do you like oranges" would be "क्या तुम्हें संतरे पसंद है"
Whenever you want to ask "what" someone does, put क्या right before the verbs. For example: "what did you eat" would be "तुमने क्या खाया" "what did you play yesterday" would be "तुमने कल क्या खेला"
I hope this helps.