Hello. Thanks for mapping.
We welcome you as a new mapper.
About highways.
Please read how to tag highways in this area and, 
How to measure the width of a trace In Ideditor:
Command Ctr+shift+M  shows the  measuring dimensions tab.
After that command, select add line.
Zoom in very far (20 - 25 mtr) so that you have a good view on the shoulders of a road.
Then draw a line between the shoulders.
You can read the value in the measurement tab. (select Metric value)
<2 mtr tag it Path
> 2 mtr tag it unclassified, residential or track depending on the situation. 
 Delete the line after measuring.
See the wiki african highways to decide which tag to be used.

https://wiki.openstreetmap.org/wiki/Highway_Tag_Africa
Best regards