How to increase maxhp of player when they get custom achievement permanently

Hello i want to give players health boost when they get the achievement i set it up so when i give myself the achievement everything working but

The hp which i gived with adding a potion effect called HEALTH_BOOST is not regenerating

i have 60 hp in total but it stuck at 20 because it wont naturally regenerates your Health

So is there anyway i can make HEALTH_BOOST potion effect's Health Regenarate or

Any Other ways to make players hp increase ?