How to say "yes" in chinese? (Mandarin)?

Good question--

Short answer: say 是 (shì) or 是的 (shì de), which is slightly more formal. Alternatively, you can also say 对 (duì (dway)) or 对的 (duì de), which means "correct".

Long answer: Mandarin doesn't have words for "yes" and "no" that can affirm or negate any question. Textbooks and teachers will tell you it's 是 (shì) and 不是 (bú shì), which is 100% incorrect.

是 (shì) and 不是 (bú shì) mean "it is so" or, "it is not so" and are only fit for confirming or denying direct assertions, such as:

Is that a hat on your head? (it *is*, it *is* not)
Are you an American? (I *am*, I *am* not)
Did your cat die in a fire? (It *did*, it *did* not)

However, there are several other classes of questions which require different answers, and the method is simple: the answer simply *re-uses the main verb in the question*, so:

Do you *have* enough money? (the correct response is "have"/"don't have") 有/ 没有 (yǒu/ méi yǒu )

Did you *go* to the store yet? (the correct response is "went"/"did not go") 去了/ (还)没去 (qù le/ (hái) méi qù)

Did you *buy* toilet paper yesterday? (the correct response is "have bought"/"have not bought" (买了/ (还)没买 (mǎi le/ (hái) méi mǎi) OR I "have" not 没有 (méi yǒu )

As you can see from these examples, the answer generally re-uses the main verb, or implied verb in the question. It may seem like a lot, but you will become used to it *very* quickly, the key is to listen to the way that native speakers around you also echo the question when answering--it will become second nature in no time.

Good luck in your studies

DISCLAIMER: no cats were harmed in the writing of this answer.

[EDIT]: I neglected to include Siomon's option: 没错 (méi cuò) (literally: "not wrong") (for questions where the answer can be right or wrong) be careful with this one, it's casual and shouldn't be used with social superiors.

你好，我是Jim

shi 是

I don't want to google translate so pls answer only if you're sure

對, 沒錯.
Pinying : dui,　mei　cuo.
Translate into English would be - Yes, that's right.
If you want to say it in simpler way, you could say either “對” or “沒錯”. But certainly the former is much better.

Just nod.