Can I add more storage for my MacBook Air 2019?

You can add external storage. That Mac has two USB-C (Thunderbolt 3) ports that would let you plug in either USB SSDs or Thunderbolt 3 SSDs. When supporting USB accessories, the ports can run at up to 10 Gb/s (USB 3.1 Gen 2 speed).

According to Other World Computing (a vendor who carries SSD upgrades for a lot of older MacBook Airs),

"Since 2018, Apple began to solder in the SSDs of all MacBook Air laptops, which makes upgrading the internal storage of these models impossible."

There are some external SSDs that are very small. For instance, the Crucial X9s, X9 Pros, and X10 Pros are roughly the size of a credit card – less than half the size of even a slim portable mechanical hard drive.

Yaaslin wrote:

can I add more storage for MacBook Air 2019

[Re-Titled by Moderator]

You can free up internal storage by following the instructions here: Free up storage space on Mac - Apple Support