But the post doesn't say that we "unlearn everything in our life" - it says we lose our memory.

Acquired behaviors (note that I won't refer to them as "learned", because the distinction made between "learning" and "acquiring" is a useful one for many reasons - I'd be happy to go further in depth here if you're interested!) are stored in different parts of the brain than what we commonly refer to as "memory".

If you're hung up on the definition of memory, we need look no further than the fact that a common synonym for amnesia is "losing one's memory". If you want to use a definition of "memory" that goes beyond what people usually mean when they say it, that's fine, but then our comments here seem to boil down to a disagreement over definitions, rather than a disagreement over empirical facts.