Concentration and Shapechange 5e [duplicate]

I’ve been trying to make use of the Shapechange spell as a 9th level spell with a Druid class, but concentration seems to be a major issue. Say I transform into a Phoenix, can I use the 3 Legendary Resistance to automatically succeed in a damaging saving throw three times to prolong the form? This would make Shapechange viable for melee characters for atleast a slightly longer period than a single turn.