Welcome to the forum. Thanks for your question.
You are of course right that HIV is far more common in parts of Africa, including Kenya, than it is in North America or Europe. But you don't say your partner's HIV status? Did you ask? Probably he has been tested, and if positive he would have told you. If he has tested negative, of course you weren't at risk.
More to the point of your question, the HIV lab tests are among the most accurate diagnostic tests for any medical condition. No matter how high the risk of HIV, the test results are 100% reliable if done sufficiently long after the last possible exposure to the virus. That interval is 4-12 weeks, depending on the specific test (or combination of tests). It is never necessary to wait 6 months; that's an outdated urban myth, left over from older tests that haven't been in use for 20 years. Even if your partner has HIV, you wouldn't need to be worried, given your negative test results.
Below is a link to a thread that discusses the time to reliable HIV test results, including the reasons that official advice remains 3 months, even though earlier testing (4-8 weeks) almost always is conclusive:
For those reasons, you needn't be at all worried. Your first test (the 48 day 4th generation [duo] test) was conclusive and the others also confirm you were not infected.
I hope this has helped. Best wishes-- HHH, MD