Your legs are still fresh and your head is full of questions. Is your rucksack sitting properly? Have you forgotten anything? Those doubts will fade with every step. It’s a long day, well over 7 hours, but the hills are nothing to worry about.
Many pilgrims take the metro for the first stretch through the city as far as Matosinhos. That saves you a lot of urban kilometres. Still, you’d miss the lovely walk out of Porto. From there, you follow the coast, with salt on your lips and the ocean beside you. At the end, Vila do Conde awaits, where there is a public pilgrim albergue. A good place to end your first day.
Take it easy at the start. The Camino isn’t going anywhere.