I am not sure what this means:
私はこの失敗を出発点としてもう一度初めから頑張るつもりです。
Here is my go at it:
This mistake will be used/made as a starting point, one more time for something or other?
It seems the issues you are having with this line may be similar to those in this other question of yours here.
I linked a very helpful answer in my answer there.
私はこの失敗を出発点としてもう一度初めから頑張るつもりです。
can be rendered roughly as:
I intend to take this failure as a new point of departure, start over, and work hard.