Hi YangYYYY,
Thank you for reaching Microsoft Community.
Based on your description, your Surface Go 2 is now only left with around 6GB of free storage even if you only have several applications installed and files are also saved mostly on the cloud. May I know first what is the total capacity of your Surface Go 2's drive? Please try checking this page also for the available disk space for each Surface model: Surface storage options and hard drive sizes - Microsoft Support
To troubleshoot the issue and to free up some space on your drive, please follow the steps provided on this page: Free up drive space in Windows - Microsoft Support
Let me know how it goes.
Kind regards,
Marrion