Your decisions up to that point count. Look it up. Basically you have to do whatever it takes to make her happy in your decisions.

Throughout the story you must make decisions around Ciri that yield positive results from her.

if you play snowball instead of drinking with her she will be alive and in avallach's room, let her do everything when she is mad

The save at eredin is too late. If you have a save just after rhe fight ar kaer morhen i would use that one. Then choose the option: "i know what might chear you up etc" when she is sad about vesimirs death. There are 4 dialogue options throughout the game which influence the ending. In 2 of those you should choose the positive options, look it up.

Thank you guys for informing

I saved right before i meet Ciri and I gotta use it and i wonder if i can skip some parts of game. I heard that it is possible to skip and I want to skip some parts

Let her go into the meeting alone too

Play snowball with ciri, wreck avallach's lab together, let her go to the meeting with the sorceresses alone, visit Skjall's grave with her, and if you took her to Emhyr, you have to refuse the coin from him. I think you only need to do 3 of these and you'll get either the 2 endings where Ciri lives

Omg why did i read the comments now i know vesemir will die

Spoiler alert!

Ask the master of mirror.