Welcome aboard! That is a very interesting portable cnc plasma cutter that I have not seen before. I did find a youtube demonstration video. Where did you buy it? I assume you are cutting hot rolled steel plate of about 1/8" thickness. I think your first attempt looks pretty good. You are cutting at 177 inches per minute. What plasma cutter are you using? I would recommend paying particular attention to your settings for pierce height, cut height, and cut speed. Your edges look wavy - but that could also be from some instability or vibration in your machine with that extended arm. For you - slower cutting speed might be better. If I were cutting your 3mm material using my Hypertherm plasma cutter, I would set the pierce height to 3.8 mm, cut height to 1.5 mm, pierce delay time to around 0.4 seconds, and cutting speed to somewhere around 3800 mm/min. You might need to slow down your cut speed do to induced vibration in your machine due to the instability of your setup. If your plasma cutter came with a manual with mechanized cutting charts, then you could refer to those for the recommended settings for your particular cutter. Good luck and keep us posted.
David
https://www.youtube.com/watch?v=XR4xg3SxoJg