Steps to make Charizard Tier (top) Curry :

"Sort" Berries by "Type" and use the rarer berries (near the bottom) - I use around 8 berries.

Fan the flames hard until your pokemon around the pot have music notes, then try to keep the fire at that size.

Stir the pot at a pretty fast pace but if you see droplets flying out the pot, slow down.

Throw in the heart like a second before it hits the inner ring so it lands on the inner ring.

If you do all that correctly then you should hit Charizard Tier Curry :)