delete wp-signup.php and wp-login.php from root folder

Don`t delete core files of wp. Just add a FilesMatch or Files directive to limit acces to it (your ip) in your htaccess file.

The following would block acces to all scripts ending in “admin.php” :

<FilesMatch "admin\.php$">
    Order deny,allow
    Deny from all
    Allow from 10.0.0.0/24
</FilesMatch>

The following would ONLY block admin.php :

<Files "admin.php">
    Order deny,allow
    Deny from all
    Allow from 10.0.0.0/24
</Files>

replace 10.0.0.0/24 with your ip range (from 0.0.0.0 to 1.2.3.4.)

tx,
how can i block the whole folder wp-admin?

i created htacces file in wp-admin folder with this code:
order deny,allow
allow from *.*.*.*
deny from all