Negative sentences are made by placing the negative 不 [bù] before the verb.
The negative 不 [bù] is pronounced with a fourth tone when it stands alone, before a pause, or before any first, second, or third tones. Before another fourth tone, however, 不 is pronounced with a second tone. In this case pinyin rules dictate that the tone mark is also changed to a second tone.
Generally Chinese does not use plurals, with the exception of personal pronouns. In the case of personal pronouns (我,你, and 他) a plural marker is always used.
The adverb 都 [dōu] always comes after the subject and before the verb. Use 都 to indicate that the verb is true for all the subject. Since 都 is a modifier, when used with a single syllable stative verb like 好 or 忙, it is not necessary to use another modifier like 很.
The adverb 都 [dōu] can appear before or after a negation. The position of 都 changes the meaning of the statement. When 都 precedes the negative (都不) it indicates that the entire subject is not the verb. If 都 follows the negative (不都) it means that the verb is not the case for the entire subject.
Mandarin has a possessive particle we will learn about in lesson 6, but in this lesson possession is indicated by placing a personal noun directly after a pronoun. To say my older brother just use the pronoun 我 [wǒ] followed by the person noun 哥哥 [gēge].