予約 and 注文: reserving a table and ordering food
Distinguish securing a place in advance from requesting goods or services in a restaurant setting.
What you secure in advance
予約 is read よやく and refers to reserving a place or time in advance. 「金曜日の夜に二人で予約したいです」 requests a reservation for two on Friday evening.
「予約を確認してください」 asks someone to check an existing reservation. Requesting and checking a reservation are different stages, so pay attention to the verb as well as the party size and date.
Choosing what you want served
注文 is read ちゅうもん and refers to requesting food or goods. 「コーヒーを二つ注文しました」 says that the speaker ordered two coffees, a completed action.
「注文はまだです」 can be used when you have not ordered yet. Being seated or having a reservation does not by itself mean that an order has been placed.
When the two actions occur together
「席を予約してから、店で料理を注文しました」 describes reserving a table and then ordering food at the restaurant. Both are actions that actually took place in the past.
注文 can also refer to an advance order, such as for a product before release, so do not equate everything done in advance with 予約. Focus on what is being reserved versus what is being requested for purchase or service.
How would you say that you have reserved a table but have not ordered food?
Show the answer and why
You can say 「席は予約しましたが、料理はまだ注文していません」. The table reservation is complete, but the food order has not yet been placed.