How to add some features to a DVD?

Hi!
I have a DVD movie with several audio and subtitle streams.
My question is how can I import one more audio and one more subtitle stream
and preserve the current chapter structure plus the same menu only with the additional buttons for the subtitle and audio streams?

There are several commercial DVD authoring programs. VideoRedo is one, there is a free trial to see if it meets your needs. The others probably have trial versions as well. There is freeware available, I can’t really recommend one, just google for a bit, you’ll need a demuxer and then a muxer. Pgcdemux and Muxman come to mind.