Did she give you a discount...,

[Silverobama]

Mandy ran a restaurant downtown. Thomas was complaining to me the bad service in Mandy's restaurant. That really surprised me because Thomas was Mandy's friend. Thomas said the food was bad and the service was bad either. I asked Thomas a question.

Silver: Did she give you a discount?
Thomas: Definitely not. She didn't allow me to use the coupon there.

Is the conversation natural?

 

[emsr2d2]

Mandy ran a restaurant downtown.

Who's Mandy?
Does she no longer run the restaurant?

Thomas was complaining to me the bad service in Mandy's restaurant.

Who's Thomas?
There's a word missing in this sentence.

That really surprised me because Thomas was Mandy's friend.

OK, but did you really need to repeat both their names?

Thomas said the food was bad and the service was bad either.

Surely you can come up with an alternative for one of the uses of "bad". It's very repetitive.
"Either" is the wrong word.

I asked Thomas a question.

Silver: Did she give you a discount?
Thomas: Definitely not. She didn't allow me to use the coupon there.

Is the conversation natural?

Your question is OK. Thomas's initial two words seem overly strong to me. Also, I'm not sure what the link is between the discount and the coupon and the bad service. I assumed he thought he would get a discount because they're friends. What is this voucher that's never been mentioned before? Why did he think it would be accepted at her restaurant?
Bad service at a restaurant is usually linked to the waiting staff or the quality of the food. I don't think I'd class them turning down some sort of discount coupon as bad service. It's disappointing, certainly. If the coupon specifically says it's valid at that restaurant, then the restaurant (Mandy) is wrong not to accept it.

 

[Silverobama]

Who's Mandy?
Does she no longer run the restaurant?

Mandy used to own a restaurant but her restaurant failed because she charged so much and offered bad service. There was also an English club in her restaurant (there was a seperate room).

Who's Thomas?

Thomas is a friend of mine and we both know Mandy.

There's a word missing in this sentence.

Thomas was complaining to me about the bad service in Mandy's restaurant. (Not sure if I'm correct.)

OK, but did you really need to repeat both their names?

That really surprised me because They're friends.

Surely you can come up with an alternative for one of the uses of "bad". It's very repetitive.
"Either" is the wrong word.

Thomas said the food was horrible and the service was awful.

Your question is OK. Thomas's initial two words seem overly strong to me. Also, I'm not sure what the link is between the discount and the coupon and the bad service.

I thought Thomas would either used the coupon or got a discount from Mandy. He told me he had spent 750 yuan for the meal.

I assumed he thought he would get a discount because they're friends.

Exactly!

What is this voucher that's never been mentioned before? Why did he think it would be accepted at her restaurant?

I forgot to mention that usually when people eat out, they'll take a look at Groupon. It's an app offering discounts or coupons, usually for two or more than two people. I think since they're friends, Thomas would at least got a discount from her.

Bad service at a restaurant is usually linked to the waiting staff or the quality of the food. I don't think I'd class them turning down some sort of discount coupon as bad service. It's disappointing, certainly. If the coupon specifically says it's valid at that restaurant, then the restaurant (Mandy) is wrong not to accept it.

Right. I forgot to say (because I want my context to be concise) that Thomas was numbering the unpleasant quality of food. He said the soup was too salty and the shrimp was overly-cooked, and so on.

Thomas said that he couldn't use the coupon because it was Valentine's Day and coupons were not allowed during those holidays but there wasn't such a rule of her restaurant. Mandy cooked up an excuse to stop him from using any coupon.

 

[teechar]

Thomas was complaining to me about the bad service in Mandy's restaurant.

Note the correction.

Thomas said the food was bad and the service was poor also. bad either.

or

Thomas said the food was bad and the service wasn't great bad either.

Do you now see how "either" is used in such sentences?

 

[emsr2d2]

Mandy used to own a restaurant but her restaurant it failed because she charged so too much and offered bad the service was bad.

Your original should have opened with "Mandy used to own/run", not "Mandy ran".
You need to practise using pronouns. You didn't need to repeat "restaurant".
Don't use "so" when you mean "too". "So much" should be followed by "that" (and more!)
I'm sure she didn't set out to "offer" bad service.

There was also An English club sometimes ran in a separate room in her the restaurant. (there was a separate room).

You already explained that it was Mandy's restaurant so you don't need to keep saying "Mandy's" or "her". You can just call it "the restaurant".

Thomas is a friend of mine and we both know Mandy.

OK. That wasn't clear. Mandy is a "mutual friend".

Thomas was complaining to me about the bad service in at Mandy's restaurant. (I'm not sure if I'm correct.)

That's correct. The word "about" was missing.

That really surprised me because they're friends.

That's much better. You could also have said "That really surprised me because he's her friend".

Thomas said the food was horrible and the service was awful.

That makes more sense.

I thought Thomas would have either used the a coupon or got a discount from Mandy.

Note the change of tense above. You can't use "the coupon" here because you've never mentioned it before so at the moment it's just "a coupon".

He told me he had spent 750 yuan for on the meal.

See above.

I forgot to mention that usually when people eat out, they'll take a look at Groupon first/beforehand.

They don't look at it when they're eating out (at the same time). They look at Groupon in advance.

It's an app offering discounts or coupons, usually for two or more than two people.

See above.

I think thought that, since they're friends, Thomas would at least have got a discount. from her.

See above.

Right. I forgot to say (because I wanted my context to be concise) that Thomas was numbering detailing the unpleasant quality of the food.

See above. He wasn't "numbering" anything.

He said the soup was too salty, and the shrimp was overly overcooked, and so on.

See above.

Thomas said she told him that he couldn't use the a coupon because it was Valentine's Day and coupons were not allowed they can't be used during on those such holidays.

See above.

but However, there wasn't such a was no such rule of at her restaurant, as far as he knew.

See above.

Mandy cooked [simply] made up an excuse to stop him from using any a coupon.

See above.

 

[Silverobama]

Do you now see how "either" is used in such sentences?

Yes, "either" is used in a negative sentence to mean "also".