Ok, the problem it's pretty clear now, but I'm not sure about what are you doing wrong. What you are trying to do is a very basic stuff that I'm sure that is working.
Try removing the transitions to the ends nodes from all your tasks. I mean, the three tasks after the fork node. Probably what's happening is that your task nodes are not waiting for completion and the first tasks that is being created is automatically ending the whole process.
Can you share some logs about the process execution?
Greetings.