The portuguese began which lasted over 400 years, and was harmful for africa.

Hey there,

Your question states: The Portuguese began which lasted over 400 years, and was harmful for Africa.

Your correct answer would be on how the Atlantic Slave Trade did these things.

The the Atlantic Slave Trade was which began over 4 centuries and was very harmful for Africa.

Hope this helps.

~Jurgen 

The Atlantic Slave Trade which began over 4 centuries was very harmful for Africa.
Hope this helps:-)