Hmmm that's a challenge, normally I advise start on longer board and then come down as you progress a lot of the early learning is about catching waves and getting and out from the break so the length has some advantage, but bigger volume boards present beginners with duck diving problems when they head out into look for green waves to surf>
The younger you are and the lighter you are, the smaller your first board can be. If you are forgoing length then you can increase volume by getting a wider and thicker board without compromising performance at this stage.
I'd avoid a fish as they are designed to perform in skilled hands in mushy conditions.
Not sure what sort of boards available to you in Portugal, if you can post a picture of a few of your selections.
I'd look to shapes like this
or these are Global surf Industry boards and they come in the full range you are thing about and 7'2" wouldbe better, they may not fit your budget so keep these shapes in mind and have a look at their website and then see if the secondhand market can give you something similar.
The learning is going to be more challenging but it's still fun.
There are also a lot of surf schools in Portugal, a friend has just come back from instructing at one I'll ask what he recommends.
That involves a question what area do you plan to surf at? That might help advise you. I think there may even be places where you can store your board so you can travel easily to the beach!
I've taken up troll hunting just for fun, instead of a rifle I'll just use a pun! 冲浪爷爷