It's possible to book here (there's availabilty, but not for every train):

https://travel.b-europe.com/dsb-rail/en/reservation-only?_ga=2.2613488.1320264495.1690703073-2054011771.1690703073#TravelWish or https://www.cd.cz/en/spojeni-a-jizdenka/api-hp/

First one easier, second one cheaper.

Which train ? It is possible that it is sold out as it's a very popular route but you should find other trains during the day.

Check availability here : https://travel.b-europe.com/dsb-rail/en/reservation-only#TravelWish (click on the price and wait until it says whether it is sold out or not)

Then buy it on cd.cz for 73 CZK (3€). It's cheaper than anywhere else.

If you have other questions, mention the train you're looking at and we'll have a look.

There are always reservation-free alternatives :

- RE Hamburg - Flensburg

- IC Flensburg - Fredericia - Copemhagen (reservation optional but recommended, 4.90€ for the journey on bahn.com)

Thank you very much to both of you taking the time to answer. 

It worked with the link  https://travel.b-europe.com

I had an over question because you seem expert. 

Is possible as a French person to book a ticket from Paris to Bordeaux with interrail pass ? 

Thank you in advance,

Cheers,

You are allowed to use a global pass on two days also in your country of residence (but these are no additional travel days).

So it doesn't matter if you're french, it's your country of residence that does count. 

If you do live in France and you didn't use your inbound/outbound days already (or you do need them to leave your country and / or to come back), it's also possible to go from Paris to Bordeaux.

But be aware that this will take one your two days on which you are allowed to travel in your homecountry.

Normally, you do use them to start your trip and to come back.