When you use 不怎么 (bù zěnme) before an adjective, it means "not very." This structure is similar to how English speakers may say something is "not very good".
Structure
When used together with an adjective, 不怎么 becomes similar to 不太, which means that the degree of the adjective is not very high.
Object + 不怎么 + adjective
Using this grammar structure is a way to indirectly or mildly state something. Instead of saying "他不太聪明" you can say "他不怎么聪明", turning a very direct statement to a milder, more wayward statement.
Examples
Zhèɡe rén bùzěnme hǎo.
这个 人 不怎么 好。
这个 人 不怎么 好。
This person isn't very good.
Wǒ juédé zhèɡe cài bùzěnme hǎochī.
我 觉得 这个 菜 不怎么 好吃。
我 觉得 这个 菜 不怎么 好吃。
I think this food isn't very tasty.
Nǐde háizi bùzěnme kěài.
你的 孩子 不怎么 可爱。
你的 孩子 不怎么 可爱。
Your child isn't very cute.
Gōnɡzuò jìnxínɡ dé bùzěnme shùnlì.
工作 进行 得 不怎么 顺利。
工作 进行 得 不怎么 顺利。
The work wasn't carried out very smoothly.
Remember that to make 不怎么 mean "not very" use it with an adjective. Using it with a verb will give it the meaning of "not often."