can you add more storage and memory to a macbook

An official authorized Apple service may offer external storage upgrade.

Storage in MacBook 2015+ 12-in Retina appeared to be 'soldered-in'.

Some third-party sources may offer upgrade parts for retina 12-inch.

The memory (RAM) also appears "fixed" or built-in, & can't be changed.

See OWC site examples Mac upgrades (link) for upgrades by model.

Good luck & happy computing!🌻🐝

Depends on the specific model of MacBook.

Some older ones will let you do that. Newer ones will not, as everything is soldered to the logic board.