+397 I know pretty much nothing about critical path analysis so this is simply a common sense view of the situation.
The problem seems to be with the join of C and D and specifically F from that point.
F depends upon D but not upon C, so activity F can be started as soon as D is finished and before C is finished.
That means you have to separate that join of C and D in some way.
I don't know how, conventionally, this is represented.
