No one is 'imposing the English language'. People are dying to learn it.
They're not eager to learn English so they can read Shakespeare. They're doing it because (as they say in the movie linked in Phat's post) they prefer employment in tourist hotels to rural poverty.
Cultures don't matter. People matter. If the people don't want their culture, or some aspect of it, then let them throw it away and pick up something they like better.
Problem is, culture comes with people. And it sounds like you're defining culture in a very consumerist way, as if the shared history of a community is just like other any item you acquire and discard whenever the mood strikes you.
The people want European languages, and European languages will benefit them most. It's time to stop the nonsense of 'preserving culture' and start helping people.
Only it's not about helping them in postcolonial Africa, it's about exploiting them. It's not as if there's a level playing field or a power equilibrium. Europeans still call the shots, and you seem just fine with that.