Welcome to the forum. Welds get to look like that when you're just starting, but get better very quickly.
The sheet looks a bit thin. Do you have any 1.5mm scrap to play with? That would be much easier. Then use either the lowest or more likely the second lowest power setting and weld a bit more slowly with some side to side movement and holding the gun in both hands (full face mask rather than handheld).
I dont have any 1.5mm scrap, I think I better get some! The top piece is 1mm and the bottom 0.6mm. I bought myself an elctronic mask which is very useful, I do like to be able to see what im doing.