Where can i sell my macbook

Try eBay or place an ad in a local newspaper.

Prior to selling your Mac, read here > What to do before selling or giving away your Mac - Apple Support

A place such as Amazon, eBay, or a nearby store which sells used Apple products. Apple may also run a recycling program in your country.

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Or Craigslist.

As recommended by most of the members, places like ebay, amazon, craigslist & of-course local news advertisement can work well.
Wish you luck!