Admin cant login

all installation is correct, but why i cant login ?

i've clear cookie and cache too

Probably you mistyped the password when you created the account. Simply delete the user/accounts/admin.yaml file and it will prompt you to recreate the account.

On a side note. The docs says we can create user manually by creating a user.yaml file and add the appropriate contains. Is there a site we can convert the password in hash?

No, you just set:

password: your_password_here

And then when you login the first time, it will automatically hash the password and remove your plaintext one.

thanks @rhukster, i've reinstall my server, from yesterday i'm trying to use nginx-pagespeed for grav server, i though it's not compatible with grav isnt it ?

It might be nginx-pagespeed, but regular nginx works fine. Have you tried disabling pagespeed?