Hi HudaThunkit,
I would read post #15 here (and the links in option 3) before trying to design your own mattress.
If I was in your position … I would lead towards one of the “choose your own layer” mattresses from one of the online manufacturers that are listed in post #21 here so you can use your own sleeping experience to decide if the mattress is suitable for you in terms of PPP instead of testing the mattress ahead of time. This way you would also have the ability to re-arrange or exchange layers if the initial combination doesn’t work well for you. Most of them also have a good return policy if all else fails and when you are considering a mattress that you haven’t tested before your purchase then the exchange or return policy may be one of the most important parts of your personal value equation.
Trying to design your own mattress without already knowing the specific design that will work best for you can be risky (and costly) unless you only make purchases from sources that have a good return policy or without the guidance of a knowledgeable and experienced manufacturer that would be able to help you make the best possible choices.
Phoenix