Dear Alison,
Congratulations on creating another branch in two trees.
The following site is one to bookmark for most questions you might raise about DNA testing:
https://isogg.org/wiki/Autosomal_DNAHowever, I agree with Martin that a child-like approach is very helpful for us newbies.
DNA testing for genealogy purposes is still a fairly recent thing made possible by the rapid fall in the time needed to analyse a sample and the associated costs. Most of the results against which you can compare yours are for residents of the United States, UK plus those former colonies to where there was systematic migration. There
are samples submitted in Eastern Europe but these are comparatively few and far between. The odds of finding a match from someone still living there are remote. However, you might find another descendent of a branch that also migrated westwards. My offspring are half-Polish and they have lots of matches with this half of the family but these are mostly in Western Europe and the US.
One of the frustrating aspects of autosomal DNA is that if only works back about six generations. After that, the "slicing and dicing" of reproduction renders any matches almost meaningless. Also, testing only finds about two thirds of the matches in any given batch of samples.
Nevertheless you will have lots of autosomal matches and somewhere in that crowd. I have found the test hugely beneficial and have found and met a whole batch of 2nd, 3rd and 4th cousins, all previously unknown to each other.
Stay calm and keep digging.
Malcolm