may I add my experience about each eather understanding in Mandarin?
In my country, Italy, there is a lot of Chinese people: in some zone of my town there are more Chinese people and Indian than Italians. jajajaj! it is a matter of fact! but the problem is NOT for them to understand me: ‘cause whatever they come from..they understand me! It’s ME to have problem to understand some of them! exactly: I can understand very well chinese women and girls when they speaks..and young boys…but not as well old men or old women. I do not know the reason but this is the true. Other experience is that, the chinese children as well the indian or black, speak italian slang! but not their mother language! So I asked to a chinese baby girl what is your name and she remained surprised! Her father answered for her! laughing ‘cause his daughter born in Italy doesn’t speak mother language!(what’s a pity!)and sometimes I realized chinese people 20 years old, born in Italy, cannot write or read Mandarin!Anyway a lot of chinese people told me to be surprised how many Italians speak a good Mandarin! And more: a lot of young chinese people speak perfect Italian!They told me as it was so difficult for them to speak, at the beginning, than to understand…while to me is the contrary: wo hui shuo han yu danshi wo dong de yi diar. So when I speak Mandarin they understand me but when they ansewer me…I rarely can undestand..ajajajaj