i have bought F.E.A.R , 3 days back , and it didnt show on my library ,

Try https://www.gog.com/account/refresh
Check if it's there now.
If not, check your Orders & settings.
If it's not there either, something might have gone wrong on the payment side. Check if the money was withdrawn.
If so, contact support.

Oh, and also check that you've actually logged into your main account.

Oh, and if you bought the game from a third party webside like G2A or something, that's your own damn fault.

The only place you're buying GOG games is from right here.

:
Did you use Boleto as payment method? It takes up to three working days to process, so check back on Wednesday.

Portuguese:
Vc comprou com boleto? Leva até 3 dias úteis pra cair, até quarta deve liberar.

Usually takes one, but he probably paid on Friday, so between today and tomorrow, it should be in his account.

Traduzindo:
Geralmente demora um dia, mas ele provavelmente comprou na sexta, então deve aparecer na conta dele entre hoje e amanhã.