@Cabrinisamuele can you provide a screen shot of how you added them into Squidguard, and Squid ACL area?
Are you are attempting to block or approve domains/urls in Squid? Are you using SSL intercept or transparent mode? Do you have cache enabled? Browser in timeout means the URL is blocked. Did you mean the problem is when you attempt approved traffic it times out? Finally, why are you using both? Example: I use Squidguard to manage my blocks sites that I want no access to for Squid behalf. What is your end goal? Is it to block those URLs? Squidguard itself changes the Squid conf file and add the blocks or approve lists, so with Squidguard already running those domains are already included in Squids config in the background.