Too much errors in Error Log (cPanel)

Hello, first of all I apologize for my English.

My site is on te next domen: https://www.prelepapoezija.com

In a Error log has a lot of errors, about 300 per hour.
My website is too slow.
I use Skirmish theme!
I have a lot of plugins, they probably mostly slow the site.

Can someone on the basis on some eroros tell me what produces them, and howe to fix them?

Some of the errors in Error Log:

[Thu Jan 15 23:46:15 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/za-tebe-ljubavi-moja/
[Thu Jan 15 23:46:12 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/za-tebe-ljubavi-moja/
[Thu Jan 15 23:46:09 2015] [error] [client 82.145.208.176] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/tama-je-padala/
[Thu Jan 15 23:46:06 2015] [error] [client 82.145.208.176] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/tama-je-padala/
[Thu Jan 15 23:45:56 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/ostali-pesnici-3/zak-prever/
[Thu Jan 15 23:45:53 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/ostali-pesnici-3/zak-prever/
[Thu Jan 15 23:45:22 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/ostali-pesnici-3/
[Thu Jan 15 23:45:22 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/ostali-pesnici-3/
[Thu Jan 15 23:44:59 2015] [error] [client 82.145.208.176] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/tag/viktor-igo-pesme/
[Thu Jan 15 23:44:50 2015] [error] [client 62.68.104.65] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php
[Thu Jan 15 23:44:37 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/ostali-pesnici-3/fedriko-garsija-lorka/
[Thu Jan 15 23:44:35 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/ostali-pesnici-3/fedriko-garsija-lorka/
[Thu Jan 15 23:44:05 2015] [error] [client 95.86.36.33] client denied by server configuration: /home/prelepap/public_html/wp-admin/admin-ajax.php, referer: https://www.prelepapoezija.com/ostali-pesnici-3/