I left out these sentences.
1) There are three main themes: forgiveness, reconciliation, and the element of magic.
There are two kinds of magic: the beneficent used by Prospero only for good purposes and the maleficent used by Sykorax to harm its victims.
Correction:
2) There are two kinds of magic in the play: beneficent and maleficent. The former, that of Prospero, is used only for good purposes. The latter is used by Sykorax to harm its victims.
3) The other two themes are linked to the end (are evident at the end of the play?) because Prospero forgives his brother for what he had done and returns to Milan.
2 is a good correction for 1.
3 is fine, and I like the "evident" wording better than the "linked" wording.