We usually believe that despite the fact that the content of our minds is only mental, we aren't Boltzman brains or live in a simulation but that there's a physical world out there with whom we interact. Do you disagree with the existence of such a physical world?

I completely agree, however you do not exist in this world, there are the world and it is arational. Everything is a map, and saying something is a map was still a map, an infinite paradox within the arational reality. Rational or irrational is a map, so is math or other types of science or of communication.

To judge how likely it is that something is true you first have to understand what's meant with the claim. Currently you seem to deal with language in a way where you don't get what's meant. It's like tax protestors in the US making claims about what laws are supposed to mean only to get imprisoned by courts when their intepretation of the meaning of language differs from that of other people. It's the same mechanism.

I don't understand at all because I am discussing the meaning of language, while you are thinking I am misunderstanding your meaning of your language? Is this the case?

Language is a map, so is saying "Language is a map". It's not the territory. Neither is "It's not the territory". Neither is "Neither is "It's not the territory"." and so forth.