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