How can I improve CACHE TTL for better mobile performance?

[Catax]

I worked a lot to help a friend to get as high a score as possible in googlewith his store

For the moment,I`m ok,but can be better (I do not understand why the score fluctuates on mobile performance, among others) :

I have this problem in gtmetrix:

this is the webiste (maybe it helps to figure how to do that 😞

artor

I try to make it 100%  😀

Any ideas how to change CACHE TTL ?? Thanks