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I see two possible problems here. Both have been pointed out but I'll address both. First, duplicate content from the same owner. If they have another site that has the same intent ... same topic ... reason for the site, you might want to merge them. I can't tell as I don't speak that language, but if they are competing sites, you don't want to pour resources into two places. That's my recommendation to the site owner. Second, the bad links. It is possible that even links that have worked in the past for other sites might be hurting this site. Again, it's hard for me to tell, but if the link brings no value other than being a link and no one uses the link to get to the site ever, you run the risk of hurting that site with that link. Free directories are prime targets for Google. I am not sure how stringent Google Greece is on this yet, but this might be an issue. With both of those things being said, if the links are hurting the site and you merge the two sites, you might hurt both by merging them. I'm sorry I can't be more explicit of the cause, but with some poor links in the past and some less than stellar links now, and a possible duplicate intent site from the same owner, either or both of those could be the cause. If it were me, start with merging the two sites. If the rankings drop for the well ranking site, clean up all poor links to either domain. If it stays down, unmerge and just let the poorer ranking domain die. Your other option is to tell the client to focus on the site that is doing well, drop this one. But be careful with the link building. You don't want the same thing to happen to the other site and that's possible.