If you like or dislike something, you can say
Me gusta la comida – I like this food
No me gusta la comida – I don’t like this food
To calm someone down, you can use the adjective tranquilo (calm), which can be translated as "That’s OK", "Don’t worry":
Tranquilo – That’s OK, don’t worry (talking to a man)
Tranquila – That’s OK, don’t worry (talking to a woman)
No te preocupes – Don’t worry
To say you’re fine, use
Estoy bien – I'm fine
You can also learn these useful expressions:
Tengo hambre – I'm hungry
Tengo sueño – I'm sleepy
Estoy cansado – I'm tired