Quitting PhD program after 1 year
The problems seems to me to have started here:
Nevertheless, I applied since I believe the value of a phd is up to yourself, not the popularity of the supervisor.
I think we can both agree that a research group in anthropology would also have very few publications related to your topic. But you can also see that doing an electrical engineering PhD in an anthropology group would be a horrible choice. They simply wouldn't have the expertise to help you and could offer no possibility to cooperate with your research.
To a lesser extent the same is true for different sub-fields of a large discipline like electrical engineering. If your topic of interest is far removed from the rest of the group, the rest of the group won't have the expertise to help you or the possibility to cooperate with you. This is a very bad thing.
One way to (partially) solve this problem is to modify your topic or switch topics to be more in line with the rest of the group. This seems to be what is proposed here to you.
Your proposed solution is to ask them to send you abroad and to continue with a topic that is not really related to their research. The question now is: why should they agree to this? They invested resources in you by either paying you or at least supporting you and spending time on you. In return you offer to do research at a different institution on a subject that doesn't really touch any of the research done at the group. That would mean that at the end of your PhD, the group would have spend (considerable) money into research they aren't interested in. That sounds like a very bad deal for the group.
If I were to summarize this: you applied and got a PhD at a group without looking at what that group does. After a year of doing a PhD there, you now realize what the group does and conclude that the group is a bad fit.
You have 2 options now as I see it: continuing with this group and focus your topic to be more in line with the research of the group. The other option is to quit now. In that last case the group would see (considerable) resources go to wast because you neglected to properly look into what the group does beforehand. This as you worried looks very bad, because why wouldn't something similar happen at a new group? If you quit, then I hope you can find a good answer to this question when applying to any future PhD.
As for the communication and language issues: I would find this a separate and smaller issue. Here an open and honest conversation about how you perceive the communication in the group and what problems you encounter could work wonders. The problems regarding research topics however is much more fundamental and more serious.
I am trying to convince them that I want to follow an other path, since the topic studied at the institute does not fit well with my topic, but they are stack with this topic, which is also studied by few niche researchers.
I wonder how you got the PhD admission in the first place. In most PhD ads I've seen, there is always a requirement for "common research interests". Some places even require PhD applicant to submit a research proposal.
The supervision you are receiving looks OK for most PhD students. The official advisor doesn't involve much, but the assistant professor is trying to work with you. You can't blame your colleague for lack of communication, since your interests are different from theirs.
In Italy and Denmark, PhD students are allowed to have 6 months internship abroad, and the trip is totally funded by the university. The majority of PhD students in other European countries do not have this luxury.
In short, there seems to be no problem in the PhD program at your group. The only problem is you don't fit them, you have different interests. Either you change yourself to fit them or you should leave. The latter option is much more difficult, and you know the grass is always greener.