Hard disk is almost full

I recently updated my MacBook Air and now every time I try and open my Outlook Email App for work I get a message that my hard disk is almost full and it says I need to work offline. The app forces me to close it after that.

I know Big Sur took up a lot of my space and I had to delete a lot of stuff I had saved just to install the app but what can I do now to free up some hard disk space??