I would like to clarify what I mean by "messages" first.
Messages - are texts realated to certain actions that get posted to newsfeed. For example the text "{userA}IS NOW FRIENDS WITH {userB}" is the message.

So action happens>>system generates messages>>system checks which language user has selected on your site>>system saves generated message in this language>>messages get's displayed in newsfeed.

That is why you are getting "problem" with your newsfeed when you use several languages.
That is how the feature was originally designed.
I have passed your concern to our product development team. They will check what can be done and whether it is possible to design this feature in another way.

Regarding notifications, what kind of email notifications you mean?

I understood your idea and have already passed it to development team. They need to take a look at whether this can be developed in another way. One of the other possible options is displaying newsfeed only in the language set as default one in admin panel. So if english is default language, everything in newsfeed will be in english. But again this might not be a good solution since then a lot of users  will not understand what is written there since they don't know english. Let's see what development team comes up with.