1. 可以刷卡吗?Kěyǐ shuā kǎ ma?
Can I use a credit card?
There is no doubt that it’s much easier to pay by credit card nowadays.
The Chinese equivalent for “Can I use a credit card?” 可以刷卡吗?
可以 kěyǐ, be able to do something.
刷卡 shuā kǎ, use a credit card.
吗 ma, is a particle coming at the end of the sentence. It indicates that this is a question.

2. 交现金还是刷卡?Jiāo xiànjīn háishi shuā kǎ?
Will you pay by cash or credit card?

Usually the cashiers would offer to say 交现金还是刷卡? Will you pay by cash or credit card?
交现金 jiāo xiànjīn, to pay by cash.
还是 háishi, or.
刷卡 shuā kǎ, to pay by card.
it’s necessary to mention that “是... 还是..shì...háishì” is a kind of selective question sentence. One person brings up two types of options and hopes that the other would choose one of them.
It’s interesting that the first 是 could be omitted. You can tell it from the sentence we gave you交现金还是刷卡?

3. 我刷信用卡。Wǒ shuā xìnyòngkǎ.
I will use my credit card.
信用卡 xìnyòngkǎ, credit card.
刷 shuā, the first tone, originally it means to brush, like 刷牙 shuāyá, to brush the teeth.
Here "刷 shuā" comes with "信用卡 xìnyòngkǎ", which means using credit card. 刷信用卡.

4. 请您在这里签字。Qǐng nín zài zhèlǐ qiān zì.
Please sign your name here.
Finally they would ask you to sign your name. They may say it like this 请您在这里签字.
请 qǐng, please.
您 nín, the second tone and it’s the polite form of 你 nǐ, meaning you.
在这里zài zhèlǐ, here.
签字 qiānzì, to sign a name.