1. I am keen on swimming - especially in the sea

  My hobby is swimming - especially in the sea 

2. She enjoys listenning to music ( She + Vs/es )

  Her hobby is listening to music

3. My dad founds on writing poems ( He + Vs/es)

  My dad loves writng poems

4. Their hobby is playing chess

  They like playing chess

5. Anna and Kim's hobby are making models

  Anna and Kim are interested in making models

I.

$\text{1.}$ 

$\text{→}$ I am really keen on swimming - especially in the sea.

$\text{→}$ My hobby is swimming - especially in the sea.

$\text{2.}$

$\text{→}$ She enjoys listening to music.

$\text{→}$ Her hobby is listening to music.

$\text{3.}$

$\text{→}$ My dad is fond of writing poems.

$\text{→}$ My dad loves writing poems.

$\text{4.}$

$\text{→}$ Their hobby is playing chess.

$\text{→}$ They like playing chess.

$\text{5.}$

$\text{→}$ An and Kim's hobby is making models.

$\text{→}$ An and Kim are interested in making models.

$\text{* Verbs of (not) Liking + V-ing:}$

$\text{→}$ keen on/ enjoy/ fond of/ love/ like/ interested in + V-ing