If you’re travelling with an Interrail/ Eurail pass, you need to pay a passholder fare of €18. You can buy this through Rail Europe.

This ICE is compulsory reservation anyway, for the French part. Regular ticket holders can get a normal seat reservation for a few Euros, but they aren’t valid with a pass.

Thanks for your reply. 

What should I do if I dont catch my train on the connection due to delay on the first train?
Do I need another seat reservation? If so, how should I get a new one for the next train if it is already full and who is going to pay for it?

Please have some margin in the first place. All German trains are late basically.

If you're about to miss a connection speak to staff onboard the late train. They might be able to issue a new reservation free of charge or at least give a proof of delay.

Otherwise speak to staff at the station (queues) or worst case, on the platform. They might allow you onboard without seat guarantee if the train is full. Do not try to board without speaking to anyone as you might face fines.

But please try to avoid these unpleasant experiences in the first place. I'd have 1h margin before the TGV/ICE to Paris.