An answer might have been less sarcastic if you had cared to tell the community that you plan to fly in from Krakow. Your questions restricts to "Hey, I need to go to Bremerhaven. How can I get there". And own research might be a burden, but is certainly educating.

And a quick look on the map or the internet would have shown you that there is an airport in Bremen allowing easy connections via FRA and MUC. A short check on Expedia would have told you that the LO/LH codeshare from Krakow is available for 443 Euro. It takes 10 minutes from BRE to Bremen Hbf by Tram and from there 52 minutes to Bremerhaven. Alternatively a taxi should get you from Bremen into Bremerhaven for about 80 Euro.

And you can certainly take the night train from Krakow Glowny to Berlin and connect there. It takes about 17 hours.

If you think about alternativ routes, boat could be considered.