since you started your promotions in facebook and there are some new players i think it would be time for strength update.
I suggest that all accounts registered from 2022 01 01 will get missions at lvl 100 and 150 with rewards: 100th lvl mission reward 100 000 Strenght added to player and for 150 lvl mission add 150 000 Strength. So there would be some kind a point to stay playing for new players
And one more thing... In my opinion make free training from lvl 70. Or at least make a mission at lvl 50 or 70 with reward Training Contract -90% 30d