On the contrary or on the other hand

On the contrary is used to make a denial or contradiction more emphatic.

• ‘Have you already done it?’ ‘On the contrary, I have only just begun.’

If we want to give the other side of the question, we use on the other hand, not on the contrary.

• The job wasn’t very interesting, but on the other hand it was well paid.

Elder and eldest

Elder and eldest can be used instead of older and oldest to talk about the order of birth of the members of a family. Note that they are only used attributively (before nouns.

• My elder sister is an engineer. / My older sister is an engineer
• She is my elder sister / older sister.
• She is five years older than me. (NOT She is five years elder than me.)
• He is the oldest man in the village. (NOT He is the eldest man in the village)

Enjoy

Enjoy means get pleasure from. It normally takes an object.

• I enjoyed the party very much.

When we talk about having a good time, we use enjoy myself/yourself etc.

• I really enjoyed myself when we went to Paris.

Enjoy can be followed by an -ing form.

• I don’t enjoy looking after small children. (NOT I don’t enjoy to look —)
• I enjoy swimming in the sea.