Your English is better than most of us here. Audio isn't really "positive" or "negative" since it's actually alternating current, but you still have to have a "positive/negative" reference for consistent wiring of connections and such, so that's why you get into the "+/-" thing.
The simple answer is that it will make no difference for a single external speaker connection. "Zip cord" or speaker wire is usually marked for polarity with a ridge or a series of ridges, or a paint stripe or dotted line, or even "+" and "-" symbols to indicate one side from the other. If not, you can always trace the wire length or use a test light or volt/ohm meter to determine the correct polarity end-to-end and mark the ends for yourself.
The usual thing is for the marked side to represent "Positive", and the smooth or unmarked side as "Negative", but since the radio audio is Alternating Current and the speaker terminals are isolated from ground, there's really no reason to specifically worry which is which. Yes, polarity does make a difference which way the speaker coil oscillates as the audio current alternates and does make a difference in "speaker phasing" for stereo equipment, but for a single speaker, it will make no difference that you can detect without test gear. Some speaker terminals are marked as "+" or "-" for the convenience of applications that do require correct phasing, but for the usual external speaker connections, it makes no difference.
With all that being said, if the audio output of the radio is not isolated and one side is referenced to ground, there's the chance that a polarity conflict could occur if you're connecting the radio's audio output to another device whose audio input is also not isolated and is referenced to ground or positive. So, a good rule of thumb is to make it policy to always make your connections referenced the same way. The usual reference is that the marked side is always "positive" (center conductor or tip of the connector), and the unmarked side as always "negative".
Did that help or make things worse?