Hi there.
First some facts. The vast majority of connecting passengers make theor connections globally. Schipol is legendary in Europe for processing connections well. Given the small size of the Dutch market they are well know for offering competitive prices in places like Northern England to take people over Schipol. There is a minimum connecting time which is assessed and monitored regularly. Of connections are made things change, but they are made. Customers missing connections is a very expensive business for airlines.
I've flown through Schiphol, returning home to Canada, many times. Always on KLM and a connection between two of their flights.
I agree with the comments above that discuss how efficient Schiphol is for connections. The airport has four wings and they're very good about whizzing you from one wing to another, by golf cart if necessary, to make a tight connection. Particularly if it's the same airline throughout (that is KLM>KLM or similar).
The one complication in this is that you're heading out of the EU on your second flight; that means you'll have to go through border control and have your passport stamped "out of the EU." That takes a bit more time than just moving gate to gate.
BUT if you let the flight attendants know, before you land from the Porto flight, that you have a tight connection to make, they are great! They will do their damnedest to see you make that connection.
We don't go through Schiphol any more; but it's only because the departures from Lisbon are at 5 am, which I hate. If they got their slots changed, in Lisbon airport, I'd be flying KLM again in a moment. Great staff, and and a very well-run airline!
P.S. If I had a choice of Heathrow or Schiphol, I'd choose Schiphol every time. Especially now after Brexit, since you'd have to do the "into the EU" entry at whatever EU airport you ended up at, if you came via the UK. And Schiphol is much more "flyer-friendly" than Heathrow, in my experience.