How to make a corner seam in sheetmetal?

Good morning,

I want to make a nice corner seam of the two flanges I made in a piece of sheetmetal, but it won’t work as the way I want to….

These are the stapes I have made:

1) Make a planer (2mm)

2) Create a flange (#1, manipulated in the sketch option so I have two bends)

3) Create a new flange #2 with a chain. (you can see in the blue circle that the corner is not nice)

4) Create a new flange #3

5) Create a new flange #4 (see that the bend is not nice, the green circle)

How can I make the two “red” corners together. (in Inventor there is a commando “corner seam”, or “mitter” ) Did I used the wrong bend commando?

My goal is to make a box with a removable top. It has to be waterproof welded after bending.

Thanks, Stefan.