Need help with mathematical function that represents progression speed

I want to get a mathematical function f(x), x should be ENERGY, that will give me Y. I will then take Y and multiply it with the energy, that will be how far a person can reach with his current energy.

I am thinking of making two functions.

  1. (UNDER 80k ENERGY):
    The function should give me an output of Y = 2.5 when i have 0 Energy. That means the multiplier will start at 2.5. (I will have a custom starting point so it doesnt multipy with Energy at the beginning and give me 0.)
    Then the function should fall to Y = 1.6 when im at 80000 Energy.
  2. (ABOVE 80k ENERGY):
    It should go infinitely up and start from 1.6. This function should be kind of steep so when i reach 300k energy i should be getting Y = 5.

The reason i think there should be 2 functions is because i think its best if they both are differently steep.

This should make it a bit easier to understand:

Ive tried help from ChatGPT but it didnt help and every function i use doesnt seem to work.

Im very open to helpful feedbacks and suggestions.