Please can you change this into your own words? Apartheid was a system of legal racial segregation enforced by the National Party government in...

What you need to do is to take the sentences and simplify them and change them around a bit.  Here's how I would do this.

Apartheid was a system in which the various races living in South Africa were kept separate from one another.  The system started in 1948 and ended in 1994.  During this time, South Africa was ruled by the National Party and that party supported and enforced apartheid.  Under apartheid, the black citizens of South Africa, who made up a majority of the population, had their rights taken away.  Apartheid helped the whites, who were in the minority, keep political power for themselves.