Hello. Thanks for mapping on this project.
When a highway you are mapping crosses other highways, you need to connect those nodes. otherwise a navigation system don't see the crossing.
About tagging of highways
Please read and follow the tagging rules on this linked document.
Decision tree, which tag to be used for roads
https://drive.google.com/file/d/1S48CEVi3yiAYWhIJu57jtLyv0ZVUbGwJ/view?usp=share_link
https://wiki.openstreetmap.org/wiki/East_Africa_Tagging_Guidelines
or
https://wiki.openstreetmap.org/wiki/Highway_Tag_Africa

Best regards
