Termination for not producing after four weeks - Welder/Fabricator Watchfire Signs Employee Review

I made mistakes (as one does for being there only four weeks). Was never once told that I needed to increase performance. WAS asked what I felt I needed to improve on. The next week, gone. It would’ve been better if we had some sort of goal board that we needed to meet. Other than that, I probably could’ve produced more signs. I had so much to learn and remember and I was trying to keep up. The supervisor even told me “Don’t worry about speed, worry about routine.” So I’m scratching my head.