Best way from Germany to Portugal and back (Without spending too much on reservations)

​@Marvin Heer You can find information here:

https://www.seat61.com/Portugal.htm

Looks like maybe normal tickets are a better idea for that route. But for this year i already got my interrail tickets (15days in 2 months + 10days in 2 months). In that case maybe a better idea to do it next year (or until i dont qualify for the youth pass anymore). Although for uk interrail would be worth it. Maybe i will combine that with something else.

The Intercity map of France might be useful. You don’t need reservations on the green routes 

https://www.sncf-voyageurs.com/medias-publics/2025-01/intercites-carte-destinations-2025.pdf

You can cross into Spain at Latour de Carol or Cerbère on regional trains, or the Euskotren (paid, but cheap) in the Basque Country. However the AVE International from Avignon will get you all the way to Madrid with a very reasonable reservation cost. 

Within Spain, it’s harder

That seems like a cheaper option then going via Paris. 10€ is pretty reasonable(cheaper then expected to get to spain) . And i like doing a short visit to switzerland. Will take a look at that option. (Via Paris would have been 52€)

I did not know that the International AVE was so much cheaper.

And the highspeed reservations in spain are atleast 10€ or less. What is the best way to book seat reservations for trains in spain, now that raileurope also charges 2€ booking fee/reservation.

AFAIK there are 3 websites where you can book pass reservations: Interrail/Eurail, Rail Europe and Happyrail. They all have a €2 booking fee, but Happyrail also has a payment fee up to 3.5% for certain payment methods, which I'm quite sure is illegal for at least Visa and Mastercard. (You can report them here. The more reports, the better.)

If you want to save the booking fees for the reservations in Spain, there is still the old-fashioned way to visit a DB ticket office. AFAIK they’re still able to do all the reservations (except the international AVE). They should even be able to issue the free Vigo-Porto reservation if you travel on that route.

Vigo can be reached directly from Madrid (AVE, 10€) or Barcelona (Alvia, on some days, 6.50€, veeery long journey)

You just need to be lucky enough to get someone who is experienced with the DB booking system.

DB can indeed still issue Renfe reservations. Not sure though if the free reservations are indeed free of charge. I did notice that Avant reservations are sometimes too expensive: €6.50 or even €10 instead of €4, but I've also seen that on Happyrail, so it may be a problem in Hermes or in the Renfe data.

From my experience with DB Reisezentrum it depends on the person you get. I have  managed to book a sleeper from Budapest to Bukarest once or a reservation foran italian ic before. But other times i was firsttold i was to early and once the booking window arrived they told me they cant reserve the train i asked a couple weeks before. But worth a try if i have some spare time at the station. 

Thank you for your help.

The one to Porto was actually free. However DB charged 4€ for the Regional/Regional Expres trains with mandatory reservations while Happyrail only charge their booking fee.