How can I replace or upgrade the memory on the Fire Max 11?

Your Fire Max comes with either 64GB or 128GB of memory; I'm guessing you have the 64GB version and want more?

The bad news here is that the memory is soldered to the motherboard in what's called a BGA (ball grid array) package that requires a hot air station to remove, not to mention quite a bit of experience in microsoldering. The cost to have that chip replaced would probably exceed the cost of just replacing the whole motherboard, but you'd have to shop around to be sure.

On the other hand, your tablet does have a microSD card slot that can hold up to 1TB of storage; that's 1,000GB, far more than you can add to the motherboard. So the cheap and easy way to increase your memory is just to add a card; the price can be quite reasonable on those cards nowadays.

If you're talking about the amount of RAM it has, both versions come with 4GB, which is generally enough for most normal operations, but the same limitation goes for it; replacing the chip can be expensive, and we don't know if the tablet's software is even capable of supporting more RAM; you could put in 16GB only to find it won't ever use more than 4. On the other hand, it could work just fine, but again the cost may be more than what you'd pay just to buy a different tablet with more RAM.