How well can you see? What style hood are you using and what lense? The other equipment and adjustments have been covered but if you can't see it will never come out right. You are definitely going too fast, but you should be able to tell while your welding. Some of that comes with experience, some from being able to see. A lot of people need a lighter lense than what comes in most hoods. I have to use an adjustable lense, on the brightest setting to see, with it I can turn out some nice beads, like hold railcars together welds, with too dark a lense my welds look a lot like yours. You have to be careful not to go too light or you will shine your eyes slowly. But you might pick up an adjustable tint hood and play with it a bit.
Also you mentioned your first project is going to be sheet metal repair, study up on it, it doesn't take much heat to warp a panel out enough to ruin it. The larger and flatter, the less heat it will take. I usually stack tack welds or very short beads, 1 inch or less, staggered 6" to a foot apart, go a little on one side, then the opposite side. This makes it faster, but keeps the metal as cool as possible to prevent warpage. There are videos on this process on you tube welding is a great skill to have, especially if you plan on doing much custom work on cars. Take your time, do good prep, and remember that a grinder makes all welds equal pretty, it's penetration and strength that matter most