I've heard that you should learn one and then the other, or it´s REALLY hard to separate them. They´re similar, and sometimes that similarity trips you up (since they're definitely not the same!). Even native speakers of one often blend the two.
When "o" is followed by other "o" sound like here, the first o does sound like an "oo" in "food". Most of the time it does sound like "oh" (the slow voice say things word by word and that why it pronounces it that way)