1. 'Are you wanting an ice cream?' - 'No, thanks.' - Corrected: 'Do you want an ice cream?' - 'No, thanks.'
2. Right now I do my homework. - Corrected: Right now I am doing my homework.
3. I'm reading a really good book about Cristiano Ronaldo. - Correct
4. Josh and Sam are hating maths. - Corrected: Josh and Sam hate maths.
5. I don't believe in ghosts. - Correct.
6. I'm sometimes play the guitar in my bedroom. - Corrected: I sometimes play the guitar in my bedroom or I am sometimes playing the guitar in my bedroom. (Both are possible here based on the context, but 'play' should not be used with 'am' in 'I'm playing'.)
7. It's sometimes raining a lot in Scotland. - Correct