In late, but as said above do NOT be afraid to start over. If you’re early in the process, it’s far easier than trying to repair something like what you showed in the screenshot. Consider that a learning or trial run.
Another good thing to do is save after every lesson and use a different filename every time. Then if one lesson gets fouled up somehow, you can go back a step rather than to the start. I know Blender has version saving, but I’m too much of a n00b to know how that works yet so I just use the old school method.
Think of it like mountain climbing. You go up a step, then fix yourself to that position before planning the next ascent. That way, if you foul up one step you won’t end up falling all the way back to the bottom!
