I think .COM and .DE are the primary extensions for German words. I got an offer recently (low $x,xxx) for Duschgel.com - and I also sold a few weeks back LCDFernseher.com for $2,500. So German.com domains are clearly in demand, especially when they refer to a popular service/product.
"ImmobilienPortal" is taken under tons of extensions (even WITH the hyphen: Immobilien-Portal). There are also countless websites containing the keywords “ImmobilienPortal”. So I guess the keywords must be pretty good.
I think the keywords have something to do with real estate but I am not sure.
Welcoming more opinions/appraisals for ImmobilienPortal (dot) com