Chosen Solution

My storage is almost full and as you can see in the screenshot. I only have 120GB of storage and half goes towards System and the other half is applications like Xcode, Unity etc. Can someone link or recommend a solution to upgrade my storage to 250GB or higher.

You are in luck. The 2018 new model of MacBook Air’s SSD is tied to SSD making it harder for end user to upgrade. Since your computer is 2017 I have linked a video for personal upgrade solution. https://www.youtube.com/watch?v=qDDbGJmx