My questions are at the bottom of the post
-in order to correct the slope would it be enough just to reposition the same screws into new holes just above or belot the existing ones?
-the corners are made like in the picture below. I am affraid that while moving the joint gutters I might crack the sealing, what do I need to do to fix it properly ?
Here is a related post that might also help you what I am trying to do How can I close and seal an abandoned downspout opening?