Хочу найти информацию о том, сколько опыта я получаю за каждый квест.

It differs, depending on what level you are when you do the quest.
Edit: Sorry I was thinking of Witcher 3, but this page might help you. http://witcher.wikia.com/wiki/Maximizing_Experience_Points

I think you would have to look in each individual .qst file
First you will need to extract the quest00.bif with UnBIF https://sites.google.com/site/csimbi/unbif (select the main.key file in the Data directory, hit read, and then extract _quest00.bif.
Search the .qst file with K GFF https://www.the-witcher.de/dlfile--id-298.html
search by value for 305442690 (PhaseActions) The value listed is the XP gain from the quest. (See Pic)

По каким-то причинам, когда я извлекаю _quest00.bif, который у меня quest00.bif, ничего не происходит? Папка куда я извлекал файл пуста.

Sorry, yes, I should have said. Right click on UnBIF.exe >properties>compatibility
Run this program in compatibility mode for Windows XP (service pack 3) (see pic)

Also, K-GFF defaults to only show .gff files, you need to select "All Files" to view .qdb & qst files. (see pic)

Когда начинаю поиск по значению, я получаю несколько найденных совпадений, какие из них мне нужны?

Then I don't know, I only got that 305442690 was the action type for XP from this Wiki page.
http://witcher.wikia.com/wiki/QST_format

However, had I scrolled further down the page, I would have seen that it lists all the quests, and clicking on the quest, shows the XP reward.

Информация там неточна, мне часто можно увидеть надписи "up to ____ XP", мне не нужна такая информация. Мне нужна самая точная информация.

I suspect that is because the XP reward can be less than maximum depending on how you solve the quest, possibly whether you found all the clues before making a decision.

That might also be why there are multiple 305442690 entries.

Maybe someone who has looked into it in more depth will come and help you.
Good luck.

Спасибо за помощь.