Welcome to the forum Petar_MK.
Unfortunately, as you have seen, Scribus currently isn't much good with hi-res displays. Even on 1080p displays the icons are a little bit too small, never mind on 4K.
The problem has been around for a while and there is a solution http://doc.qt.io/qt-5/highdpi.html
but it can only be addressed if the developers adapt the code (and I've no idea if it covers Linux which is a significant Scribus user base).
The quick fix that's available seems to have display issues that probably won't be good for a graphical application like Scribus so a lot of the code would need to be properly adapted and tested.
Having said that, if you'd like to help with testing a version that can cope with hi-res I'm sure the developers would like to hear from you (although I've no idea if they have plans for one at the moment).