Chinese sentence structures vary depending on the tense being used. In the present continuous tense, the structure involves the subject followed by "在 (zài)" and the verb, which signifies an ongoing action.
As mentioned above, 吗 is a question particle that is used to turn statements into yes-no questions.
你是李先生吗?
Nǐ shì Lǐ Xiānshēng ma?
Are you Mr Li?
你会中文吗?
Nǐ huì Zhōngwén ma?
Do you speak Chinese?
present perfect
我已经看过。
Wǒ yǐjīng kànguò.
I've already seen it.
我听说过。
Wǒ tīng shuōguò.
I've heard about that.
我试过。
Wǒ shìguò.
I've tried that.
The particle 过 (guò) indicate that that verb was done or experienced in the past. In English, the equivalent would simply be “have”, e.g. in “I have done that”, “I have eaten”, “He has seen it” and so on.
[subject] [verb] 过
future simple
sub. + 会 (huì) + v. + obj.
Wǒ huì kàn diànyǐng.
我 会 看 电影。
I will watch a movie.
present continious
她在穿衣服 = She is getting dressed, while 她穿着衣服 = She is dressed.
Structure: Subject + Verb + 着 ZHE
他穿着一条浅蓝的衬衫。
Tā chuānzhuó yītiáo qiǎn lán de chènshān.
He is wearing a light blue shirt.
正在 (zhèng zài) is used instead of 在 (zài) to emphasize that the action is happening right now.
Structure: Subject + 正在 + Verb + Object
我们正在开会。
Wǒmen zhèngzài kāihuì.
We are in a meeting.