When something ISN’T AS GOOD (PRETTY, FAST..) AS something else, we use 没有 /méiyǒu/ instead of 比 /bǐ/
EXAMPLES
America isn't as big as China.
美国 没有 中国 大。
<Měiguó méiyǒu Zhōngguó dà.>
This isn’t as good as that.
这个 没有 那个 好。
Zhège méiyǒu nàge hǎo.
My Chinese isn't as good as his.
我的 中文 没有 他 (的) 好。
<Wǒde Zhōngwén méiyǒu tā hǎo.>
Her hair isn't as long as before.
Chinese food isn’t as good as Japanese food.
中国菜 没有 日本菜 好吃。
Zhōngguó cài méiyǒu Rìběn cài hào chī.
Chinese isn't as difficult as Japanese.
Beijing isn't as safe as you think.
My Chinese isn't as fluent as his.