my old macbook air keeps saying my disk is full even though i have moved most things to icloud

my current macbook says i have 1.7 GB available of my 121 GB of flash storage. I tried managing storage and clearing up space by moving documents and most things to iCloud (which I still have a lot of storage on) but after a few weeks here we are again. I can't download anything because it says there's no space on my Mac. What should I do? Will uploading everything to an external hard drive work?