I saw that she was giving a concert in Portugal this summer and decided to visitattend it.

OnAt the festival there were quite a lot people with dark clothes, with piercings, and who looked interestingly looking people.

The concert went really well and I was all over the moon I managed to visitattend it.

I liked it so much that I've already bought tickets for the next year's concert in Austria.

Soap&Skin is the name under whichstage name of Austrian musician Anja Plaschg is performing.

More concise and natural.

I like her music for being sad and depresseding.

Because of her, I decided to pick up playing piano, since I wanted to play her songs.

I saw that she was giving a concert in Portugal this summer and decided to visit itgo.

The concert was part of a goth festival, which was quite surprising, because I don't really think her music suits it well.

OnAt the festival were quite a lot dark clothes, piercings, and interestingly -looking people.

The concert went really well and I was all over the moon that I managed to visitattend it.

I was grinning constantly during the concert because I was so happy.

Nothing wrong with what you wrote, but I would take it out since we already know what you're talking about.

I liked it so much that I've already bought tickets for the next year's concert in Austria.

I like her music for being sad and depresseding music.

An alternative word for "depressing" is "melancholy".

Because of her, I decided to pick up playingthe piano, since I wanted to play her songs.

It doesn't sound right to me to say "pick up playing".

I saw that she was givingill play at a concert in Portugal this summer and decided to visit itattend.

Music artists do not "give" a concert.

You do not "visit" a concert.

The concert was part of a goth festival, which was quite surprising, because I don't really think her music suits itfitted in very well.

The sentence is fine from a grammar perspective but "suits it well" didn't sound right to me.

In English, we have the phrase "fit in" which sounds a bit more natural:
https://dictionary.cambridge.org/dictionary/english/fit-in

OnAt the festival, there were quite a lot dark clothes, piercings, and interestingly looking people.

The concert went really well and I was all over the moon I managed to visit itget tickets.

Again, "visit" is not used with a concert.

I liked it so much that I've already bought tickets for theanother concert next years concert in Austria.