礼貌的拒绝 How to turn down somebody politely

Wǒ zuìjìn hěn máng, wǒ méiyǒu shíjiān.
我最近很忙，我没有时间。
I'm really busy, I don't have time.

Wǒ duì zhège bùgǎn xìngqù.
我对这个不感兴趣。
I'm not interested in it.