Coupons online

My friend's birthday is in on August 8th (if you say the date together with the month then you should use the preposition "on", if it is just the month then you should use in, e.g., I was born in May, but my birthday is on the 13th of May). We went to a nice Chinese roast duck restaurant yesterday. Before we went there, we checked for coupons online. We bought a 238 yuan coupon which (it is better to say the coupon which was good for 6 dishes instead of contains, since it sounds more natural) contains 6 dishes and a roast duck set. It is was (since you describe a past event) a really lavish meal that we couldn't (better to say we couldn't finish instead of we couldn't eat that much) eat that much, we had one dish we even didn't try it (there was even one dish that we didn't try). What should we do with that? (I am not sure what you wanted to say with the last sentence:))
Many coupons online it looks very seem to have a very reasonable price. But in reality it is not always like that (it will be more logical to say something like this ) we often buy a coupon online that we think we can save money with, but we usually ended up by buying too much food and wasting our money.