From what I know there is no legislation for crypto profits yet, there is alot of talk about it but nothing fixed yet, still there are allways loopholes that can work both ways, either exempt you from taxes, or force you to pay taxes, it all depends, but as a foreign individual, it is easier to go on the first loophole
Just get some portuguese lawyer and let him know about your situation, the bank you choose might even help you lool, and Welcome to the Portuguese way.