It's really hard tofor me to choosinge a favourite song because there are lots of them and there are none of them at the same time.

Music helped me a lot during my teenage ageyears, Iut was difficult tofor me to feel comfortable in a new class with new classmates and many things about my body that I didn't like.

Then, during weekends, I loved to listen to CD's in my room, sing and forget everything around me.

So, connected to this memory, I remember a song called "Volver a disfrutar" from the spanish band "El canto del loco".

Music as a rRefuge

title case

It's really hard to me choosing a favourite song because there are lots of them and there are none of them at the same time.

also: it's really hard for me to choose a favourite/favorite song...

Music helped me a lot during my teenage ages, Iyears, because it was difficult tofor me to feel comfortable in a new class with new classmates and many things about my body that I didn't like.

maybe consider something like:

...to feel comfortable being in a new class and noticing many things about my body...

TBack then, during weekends, I loved to listen CD's in my room, sing and forget everything around me.

"then" can be a bit ambiguous at times, but "back then" always refers to a past era

So, connected to this memory, I remember a song called "Volver a dDisfrutar" from the spanish band "El cCanto del lLoco".

tried to add in standard capitalization conventions

It was a super energetic song that I enjoyed a lot and that made me feel really happy in thate moment.

"I enjoyed a lot and made me" sounds to me like "I enjoyed a lot" and "I made me"

"I enjoyed a lot and that made me" sounds like "I enjoyed a lot" and "the song made me"

It's really hard tofor me to choosinge a favourite song because there are lots of them and there are none of themt many at the same time.

Really close on the first bit, on the second correction I assumed you wanted to say that you do not have many songs to choose a favourite from.

Music helped me a lot during my teenage ages, Iit was difficult to me to feel comfortable in a new class with new classmates and many things about my body that I didn't like.

Good English just added an extra capital.

Then, during weekends, I loved to listen CD's in my room, sing and forget everything around me.

Remove the comma after then

So, connected to this memory, I remember a song called "Volver a disfrutar" from the spanish band "El canto del loco".

Same here