In Europe most travel agents know nothing about rail travel. It is has become so easy now to book and print tickets online. Beside Deutsche Bahn, there is Trainline (best for France, SNCF can be difficult) and I have used OBB (Austria) the Czech and Italian rail companies. Last year I booked journeys online throughout England and Scotland but you need to pick up tickets at the station machine. If you feel lost go to Man in Seat 61 https://www.seat61.com
It is a mine of information about world train travel and the owner is very helpful if you contact him and he does it as a hobby.
Do not use RailEurope. They were good 15 years ago but now they are a ripoff.
In the UK I have recently booked tickets with the train operators direct. I then get PDF "print at home" tickets which can simply be displayed on a phone. The best thing is booking 84 days before travel, when there are a small number of tickets available at big discounts. A few days ago on the day booking opened (3am UK time, about midday here) I bought 2 first class tickets Edinburgh-Birmingham at a price about one-third of the regular standard (economy) fare. The same thing happens in Europe of you book with the railways - discounted fares when bookings open, which might be 30, 60 or 90 days depending on the country. I've bought tickets with the German, French, Spanish, Portugese, Italian, Danish, Swedish, Norwegian and Finnish railways in the last couple of years. All at a good discount, and generally with seat selection. In one or two places I needed to print the tickets at a station (in France) but that was no big deal - you can collect all of your tickets for a country at one station, not even one you are using if there is a convenient station to your accommodation. It's very easy to book your own train travel. In 2017 I booked Copenhagen-Berlin via Hamburg and the ferry with DSB (Denmark).