Remember that we cannot ever overgeneralize an entire population of a country, but in general you will find that the Congolese people value others more than most anything, including themselves. Here is where we get into the kinds of cross cultural differences that can result in misunderstandings, and here is also where it gets fun!
One of the best ways to examine culture is to look at your own culture first. Americans tend to put a lot of value on efficiency, timeliness, and the individual. In contrast to this, the Congolese put a lot of value on people (those around them), family, and community. Because the Congo is largely a communal society, you will find that the desires and needs of family, friends, and colleagues will be expected to come before those of the individual.
As a rule of thumb, keep this in mind:
Others > Self
Community > Individual
People > Schedules
On the surface this may not seem incredibly important, so let's apply it to a plausible real-life situation!
Suppose you have planned to meet with a new friend/colleague for the afternoon meal at 2:00p.m. You've arrived a few minutes early just in case, and wait for their arrival.
Over thirty minutes have gone by and you're still waiting - what do you do?
In America this is usually considered to be very unacceptable. In Congo, you should expect that your lunches/meetings will end up starting later, rather than early or on time. The Congolese like to truly enjoy life, and part of that means navigating through their day-to-day with flexible schedules and little rushing. Try your best not to react in the same way you would at home - you are a guest and you must respect these kinds of differences, even if it means making minor changes to the way you approach scheduling, social interaction, business, etc.
There are many reasons your new friend might have been late. Perhaps he/she had an appointment beforehand that was allowed to run much later than planned? This is a likely reason, because Congolese people don't "get down to business" in the same way that we do - remember: people > schedules. It is possible that your friend may have spent a lot of their time talking about personal topics like family and simply life in general.
Your new friend might have had a personal or family emergency that held them up, causing them to be late or miss the date entirely. What constitutes an emergency? Do not be surprised if it isn't synonymous with the kind of emergency you might consider a viable excuse for missing an appointment! Americans tend to place their business/schedules at a higher level of importance than the Congolese ordinarily would - remove yourself as much as possible from your own cultural understandings and be considerate to the culture of your new friend.
It will be very rewarding!