Learn Turkish: Siparişi bugün teslim ettin mi? - Did you deliver the order today?

To ask a past tense yes/no question, you take the complete past tense verb and add the question particle separately. Here, etmek (to do) becomes ettin (you did). Then you add the question word mi. Notice a big difference from the present tense: in the past tense, the personal suffix -n (you) stays on the verb, it does not attach to the question particle!

Why is there an -i at the end of siparişi?

The word for 'order' is sipariş. We add the -i ending because it is the specific, direct object of the verb—the order. This is called the accusative case. If it were just a general, unspecified order ('Did you deliver an order?'), it would just be sipariş without the ending.

Why are there two words for 'deliver' (teslim ettin)?

In Turkish, many verbs are formed by combining a noun with a helper verb like etmek (to do/make). Teslim means 'delivery' or 'handing over', so teslim etmek literally means 'to make a delivery'. In the past tense for 'you', it becomes teslim ettin.

Could I put bugün at the beginning of the sentence?