Q: how do i clean up my macbook air safely

See especially "Freeing up disk space" here:

OS X: What is "other" space in About This Mac? - Apple Support

It's best to describe the functional problem, if you have one, in as much relevant detail as possible, rather than to say what you think is causing it or how you think it should be solved.

Certainly DO NOT use any so called 'cleaning' or 'performance' applications.  They can corrupt and damage your MBA.

Download from the Internet OmniDiskSweeper and Grand Perspective (both free) and open them. They will show all of your files and the respective sizes. Transfer to an external HDD or delete files you no longer want on your MBP.

Do not forget to empty trash. Only then is space allocated for new data.

https://www.omnigroup.com/more

http://grandperspectiv.sourceforge.net/

Ciao.