Attend, but try to take advantage through initiative.
Should I attend group meetings?
Yes, even if they suck. And it sounds like your group meetings do suck. (I'm not sure what you mean by economic issues - those actually sound interesting to me; but the rest of it.) If for no other reason - for upkeep of your social and formal relations to group members; and to pick up on interesting tidbits of news.
I was in a research group once which was similar: People would say almost nothing that helps anybody else, and wouldn't even ask for help or collaboration themselves. So it was a bit like prisoners going through their roll call. Plus, accomplished, senior researchers would say how they have a paper here, and a paper there, and some prestigious visit or duty elsewhere, an appointment, etc. - and I would get bummed out.
There are only two PhD students.
That can be intimidating, since you take half the "heat"... but on the other hand, it means that it is easier for you to bring up issues in the name of your academic "class".
Which brings me my next point: Don't wait for others to ask you things at the group meeting. Try to use it to your advantage. Examples:
- Bring up a technical subject about which you don't know who to consult - even to the point of putting up a couple of slides or doodling on the whiteboard; at the point where you're stuck or things get hairy, ask the room for pointers. Obviously they wont give you a lecture about it on the spot, but it's quite likely you'll get references to papers, or webpages, or offers to come talk to them about it, or they might even tell you to talk to someone from another department.
- Discuss an economic issues that Ph.D. candidates face (without making it entirely personal).
- Talk about an interesting piece of relevant news - maybe something your read on HackNews; or even something that's... this is a bit delicate to phrase... somewhat political but not hard-core partisan, and relevant to academics.
- Suggest a subject (or a guest) for a colloquium or other kind of talk (not one to be held at the group meeting), see what people think, and whether someone else would be interested in helping you set this up.
- Ask someone to elaborate on something they mentioned in passing, which is potentially interesting to you.
Since the first group meeting I have felt very bad because all I could say was that I was reading articles, I had not started my experiments. Then I started my experiments, and our group leader asked me 'are you still in the lab?' It was like pinning.
Think about what would happen if, instead of him asking you, you would have used your turn to say: "I want to ask you guys about this problem I'm stuck with in the experiments. Blah blah blah." - essentially you would be talk about the same thing but the atmosphere would be totally different, not like an interrogation.
I am doing my doctorate in Germany and as someone from Bosnia, I don't know their culture.
(nods head) ah, that's a lost cause, there's German culture overall, there's regional culture, people are from different regions, personal affect channels culture differently. If you try to figure out "the culture" you'll probably just get a headache. Or, I don't know, maybe people who did their Ph.D. in Germany will tell you something else.