When something ISN’T AS GOOD (PRETTY, FAST..) AS something else, we use 没有 /méiyǒu/ instead of 比 /bǐ/
EXAMPLES
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.
This isn’t as good as that.
这个 没有 那个 好。
Zhège méiyǒu nàge hǎo.
Their relationship isn't as good as before.
Her hair isn't as long as before.
My Chinese isn't as fluent as his.
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.>
Beijing isn't as safe as you think.