We have so far picked up 7041 kg garbage (with your help 48kg) – help us pick up more

Bottle post from 1999

We found a message in a bottle from 1999 when we where out planing a cleaning!

The story:
After a walk we came to a place where humans rarely sets a foot,

We scout along the coast where we see a lot of debris. I get a glimpse of a heavy litter in a mountain quarry that catches my attention. I go there and sit down on my knees and start digging up some plastic bottles. Every plastic packaging I take up I read the table of content to see where the garbage comes from, much had flowed from many countries around Europa even some were from Sweden to.
Then in that moment I find myself holding a bottle in the hand that has a letter in it!

WE HAVE FOUND A MESSAGE IN A BOTTLE!
We fold up the letter carefully and togheter we succeed in deciphering: (Translated from Swedish)
Hello hello hello hello
This is Linnea
What’s your name?
What’s my little sister’s name?
Figure it out
Elephant
And
1999

Hello Linnea, my name is Filip and we found your latter year 2019 on Tjörn.

It’s a riddle so help us solve it!