nǐ / fàng / xīn / wǒ / bāng / guò / nǐ / de / máng / bú / huì / bǎ / zhè / jiàn / shì / wàng / le

你放心，我帮过你的忙，不会把这件事忘了。

Don't worry; I have helped you before, and I won't forget this matter.