[Koha] koha problem

[regina kivuyo]

when i request koha through web it give the error
Internal Server Error

The server encountered an internal error or misconfiguration and was unable
to complete your request.

Please contact the server administrator,
webmaster at library-HP-Pro-3400-Series-MT and inform them of the time the
error occurred, and anything you might have done that may have caused the
error.

More information about this error may be available in the server error log.

Additionally, a 500 Internal Server Error error was encountered while
trying to use an ErrorDocument to handle the request.

when i check /var/log/apache2/acces.log
:46.0) Gecko/20100101 Firefox/46.0"
127.0.0.1 - - [01/Jun/2016:02:51:16 -0400] "GET / HTTP/1.1" 200 485 "-"
"Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:46.0) Gecko/20100101 Firefox/46.0"
127.0.0.1 - - [01/Jun/2016:02:51:16 -0400] "GET /favicon.ico HTTP/1.1" 404
498 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:46.0) Gecko/20100101
Firefox/46.0"
127.0.0.1 - - [01/Jun/2016:02:51:16 -0400] "GET /favicon.ico HTTP/1.1" 404
498 "-" "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:46.0) Gecko/20100101
Firefox/46.0"
192.168.19.1 - - [01/Jun/2016:03:01:11 -0400] "GET / HTTP/1.1" 200 429 "
http://wi-fi.saut.ac.tz/login" "Mozilla/5.0 (Windows NT 6.1; WOW64)
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36"
192.168.19.1 - - [01/Jun/2016:03:01:11 -0400] "GET /favicon.ico HTTP/1.1"
404 447 "http://192.168.19.199/" "Mozilla/5.0 (Windows NT 6.1; WOW64)
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36"
192.168.19.1 - - [01/Jun/2016:03:01:26 -0400] "GET / HTTP/1.1" 304 155 "-"
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko)
Chrome/50.0.2661.102 Safari/537.36"

how to solve this problem
thankx
-- 
regina