Do you have anything for a bad stomach?
这里有治胃病的药吗？
A Can I help you?
A 您需要什么？
B I think I ate too much. Do you have anything for a bad stomach?
B 我想我吃得太多了。你们有治胃病的药吗？
A May I ask - do you have a pain in your stomach or a general stomach ache?
A 我可以问一下——你是胃痛还是肚子痛吗？
B I think I have a stomach ache.
B 我想我是胃痛。
A Then I recommend you take this. Twice a day. Take it with a glass of water.
A 那我就推荐你吃这个药。一天两次。用水服用。
B Thank you very much.
B 非常感谢。

Notes注释
1 If you feel just slightly unwell, you can ask a pharmacist for a remedy. For example, a stomach ache: Do you have anything for a bad stomach? / Do you have anything for a bad stomach? Do you have anything for a headache? / Do you have anything for a headache?
如果你感觉有一点不舒服，你可以到药店咨询服用什么药。例如，当你胃痛的时候。Do you have anything for a bad stomach? /你们有治胃病的药吗？Do you have anything for a headache? /你们有治头痛的药吗？
2 A doctor or a pharmacist may ask you to explain exactly what is wrong, for example, whether you have a pain / a pain or an ache / an ache: Do you have a pain in your stomach or a general stomach ache? / Do you have a pain in your stomach or a general stomach ache?
一个医生或者一个药剂师可能让你解释你究竟哪里不舒服，例如，你是否感觉a pain / 疼痛或者an ache /疼痛。Do you have a pain in your stomach or a general stomach ache? /你是胃痛还是肚子痛？

Key phrases and sentences
Can I help you?
I think I ate too much. Do you have anything for a bad stomach?
May I ask - do you have a pain in your stomach or a general stomach ache?
I have a stomach ache.
Then I recommend you take this.
Twice a day. 
Take it with a glass of water.
Thank you very much.

您需要什么？
我想我吃得太多了。你们有治胃病的药吗？
我可以问一下——你是胃痛还是肚子痛吗？
我想我是胃痛。
那我就推荐你吃这个药。
一天两次。
用水服用。非常感谢。