Low disk space when i had 50 gb the day before

So a few weeks ago i got a warning and it said low disk space,i didnt think much of it, when the day before i had like, 50GB how to fix because i tried to install unity and this is annoying, plz help i am on an asus laptop with 64 gigabytes of storage

Can you please follow this Thread:

There are various methods described which can help you to gain back some space on the disk.