I have a 240GB SSD and never used more than half of it. About 2 weeks ago, I switched from iPhone to Android and downloaded some programs to access and store phone stuff. I don't know it it has anything to do with my problem, but yesterday I noticed that I'm getting warnings that my drive is almost full!
I'm still not sure where the SSD comes into things? Are you connecting it to the phone?
If not then what is the SSD connected to? (What computer, what operating system?).
We don't/can't know just what you have downloaded/installed.
For the phone have you run CCleaner for Android to see if it will free up space for you?
Then I would get Malwarebytes for Android (Free) on the phone and run a scan to see if anything you have downloaded/installed is malicious. (or just dodgy).