How to bring back search form in header?

Hello - greetings! I find it hard to bring back my search form on the top right of the header. I think I removed it a while ago and I found several postings how to do it, for example by adding customized css. Using catch responsive pro - website johngather.de I would appreciate any help, how to bring it back.  I am ready to directly edit or at least to look at style.css files or any other file, where the "customized css" lands, to check if the added coded can simply be removed by hand.  But my understanding of the internal dependencies of these files is zero. Can you help me on my way? Thanks, John