When something ISN’T AS GOOD (PRETTY, FAST..) AS something else, we use 没有 /méiyǒu/ instead of 比 /bǐ/
EXAMPLES
Chinese isn't as difficult as Japanese.
Their relationship isn't as good as before.
America isn't as big as China.
美国 没有 中国 大。
<Měiguó méiyǒu Zhōngguó dà.>
My Chinese isn't as fluent as his.
Beijing isn't as safe as you think.
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.>
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.