He core and H shell burning with expansion of outer layers. He ignites in core H burning shell. Now the life is fundamentally different. Now carbon burning can start because core temperature is greather than 600 million K due to stronger gravity. Then also oxygen fusion neon fusion Mg fusion Si fusion.
Heavier elements are deeper in.
Each new type of fusion burning goes faster and faster and supports the star for less time. He burning - 1 million years. Si burning - 1 week. Even though the core temperature is 6 billion degrees. The core of the star is squeezed incredibly tightly by gravity.