Reevaluate your 'friendship' with this guy. Is it worth the pain of dealing with someone so lacking in tact? You are not likely to change him.
Do a lot of research on cycling and techniques, both for go fast(road)and touring. Big differences. Learn the language of cycling. Check out
www.crazyguyonabike.com for touring related cycling. Search the journals for 'Austria.'
Fit is First when it comes to selecting a bicycle, especially one you intend to ride for hours at a time, and doubly important for a diamond frame. Get advice about this from your local bike shop and/or experienced, tactful cyclists. Not from your 'friend.'
Like any aerobic activity, the muscles involved must be conditioned/strengthened for maximum performance. This can take many weeks of riding for peak results.
Recumbents are inherently more comfortable than any DF(diamond frame.) A conditioned rider can easily keep up with a roadie(go fast fellow.) Two wheeled short wheel base recombents are the fastest. Long wheel base recombents are more commonly used for touring.