It is true that a lot of cultural aspects of Africa have been lost, most specifically, religion.
If we look at imperialism, its height came after the main period of African slave trade (second answer is false).
The tribal conflicts are still very ripe in Africa, and often they're fueled by the carefulness boundary drawing of countries in Africa- the third answer is false.
More self-rule is also false, if anything, imperialism brought less self-rule