I have seen a website patent which is granted in US. My question is this patent valid only in US or other countries too? If I make a same website in Germany, then I am infringing their patent?
A US patent only protects an invention in the United States. I checked on The Lens and couldn't find any equivalent world patents in this patent's family. That said, there potentially could be an issue if your website were available to US users. I am not a lawyer so I would recommend you check with one before launching your website. Also, you should be aware there is always the potential for other relevant patents.
"you should be aware there is always the potential for other relevant patents."? by MrEric Shain might be there might be other patents which might claim the process for example US 9026942 B2 is a family patent which was granted before this US 9401941 B2 similarly there might be patents from some other applicant which might have claimed the subject matter. It's suggested to meet patent attorneys before launch of the website in your country as they would be good resource.