Project dragon z takes place after the events of super, 2 years after.
(Warning for some people. This could cringe you while reading this. Please change the strong whenever you like.)
Everything was normal untill all of sudden a mysterious sayain crashed there
With his empire (much like frieza but wants to rebuild his clan).
The mysterious sayain has a darkness spell that can be used once. (That being the future Vegeta was darkness spelled by him)
Then Goku (who is flying on flying nimbus) was going to see krillin with Tien and yamcha to see them again after 2 years of training (much like piccolo if saga at the beginning) untill he sense a very strong ki (mysterious sayain) and then he sees a figure whooshing passing him.
And so he try to get every Z fighters and friends for a meeting.
And then after Goku tells situation they all agree (well for some I think)
So the z fighters was fromed again.
Goku and the fighters must have to stop the mysterious sayain before the world gets doomed and destroyed.
(God please help me to take down the cringes)