I have Darkrai since 2020 but idk why I can't do mega ganger quest the spirit says the force is too strong to enter 🙂

You probably didnt beat Umbra in the Dark Realm as it was optional to do.
In that case you would need to repeat the Dark Realm quest and beat Umbra this time. If you want to go back to the Dark Realm you need to first defeat the Horon boss north of Necropolis in the Dark Valley, make sure to beat him without one of your pokemon fainting. Then you will be able to re-enter Alucards castle where you can access the dark realm again after beating him while having a pokemon with the move Miracle Eye in your party.

1 minute ago, Norex said:

You probably didnt beat Umbra in the Dark Realm as it was optional to do.
In that case you would need to repeat the Dark Realm quest and beat Umbra this time. If you want to go back to the Dark Realm you need to first defeat the Horon boss north of Necropolis in the Dark Valley, make sure to beat him without one of your pokemon fainting. Then you will be able to re-enter Alucards castle where you can access the dark realm again after beating him while having a pokemon with the move Miracle Eye in your party.

Do I also need poke with future sight?or just only miracle eye is fine 🙂

I have the same problem 

56 minutes ago, 98sky said:

I have the same problem 

And the same answer above already, good luck!

If u just need to beat gengar

 

Beat horon

Beat darkrai at alucard castle(bring miracle eye)

Find all 5 poke

Leveling a bit

Find umbra, kill umbra

Go out (suicide,surrender,relog)

Gengar chess open