Just like anywhere else in this world; No seats left=you stand. In these trains all seats have small screens that show between which 2 points the seat can be claimed. Empty=free.

Plus that this is a not direct link: the direct IC trains Ams->B run ev 2 hours, take slightly less time and no change-but you can if wanted to even shorten this trip. From AMS on the odd hrs: 7-9-11 etc.00

How ´full´ these trains are are very much depend on day of week and time of year. you CAN REServe, to have peace of mind, for just 4€, for even the 2 trips, on bahn.de-choose ;´seat oinly´ NO refund when plans change!

Thanks for the reply, I am actually on a very tight trip doing 6 countries in 15 days. So, better to be on the safer side and get a reservation, but some trains have like 5 changes, so getting like 5 reservations will be very expensive and not feasible. Any advice how to avoid this situation as I have to take the earliest trains possible even if that means more changes.

Once again thanks for replying.

If you can book a reservation via Deutsche Bahn (bahn.com - seat only), than you pay 4€/trip. This means if you change trains 0 times or 11 times you pay only 4€/trip for all reservations.

How do I Add my discount of Eu rail Global pass on DB as it is easy to do on OBB?

Click on "Seat only".