How do I solve the "Shopper Unsatisfied" and "We need money" problems?

"we need money" - solve this one first. This message means there are residential workers which cannot find work. Switch to residential view and look for the buildings with low money bars. Add industrial zones to your city for workers from those buildings to reach.

Another possibility is traffic (even foottraffic). Each worker makes two trips. They start in the residential building that spawns them and travel to the closest place of work (industry, commercial, service or specialization). After work is complete they travel from work to the closest place of residence to drop off the money. Workers do not return to their residence of origin. As buildings fill up, the next workers move to the next building - musical chairs style. If workers don't make it back to residential buildings before the next shift (6 o'clock) - they'll start occupying the void left by that shift. This means that some buildings may not get returning workers - and will not get money. Watch worker return paths and clear up traffic. A clear thru road can get a car from one corner of the map to the other corner in 30 minutes.

"Shopper Unsatisfied" - this means that a residential shopper cannot find a commercial building with a matching wealth level that has goods.

First - goods: switch to commercial view. At 6am and 6pm goods will automatically generate at the commercial buildings. The shoppers will come from their residential buildings and buy those goods. If the all of the commercial buildings run out of goods, then you're left with unsatisfied shoppers. Add more commercial buildings.

Note: If you have sold out of goods at 5:30 PM, but have not sold out of goods at 5:30 AM, you should instead add park capacity to satisfy those daytime shoppers. Most parks are open during the day and closed at night. If you add Commercial instead, you'll wind up with unsold goods at night because there are fewer shoppers at night.

Side note: goods have nothing to do with freight. They are two independent systems.

Second - wealth matching: residential agents have a wealth level. The store they buy goods from must match that wealth level. Click on population at the bottom of your screen and switch to details to see the numbers of each wealth class of shopper. Most likely, you have some $$ residential shoppers, but no $$ commercial districts. Add some parks near some commercial buildings to cause them to upgrade to $$. Then your $$ shoppers will go there.

I discovered this video today.

He explains quite well the 0% unemployed math vs the true facts about your citizens.