Online.top-games.fun is an adware that will attempt to commandeer your browser search and homepage. It will pose as a pop-up for a fake game advertisement then it will redirect you to malicious websites to get money from you or infect your computer further. .
The adware installed on your computer may also prevent you from changing your settings back. It will continue to monitor your browsing activity and will load tons of pop-ups related to the sites you visit. Online.top-games.fun is usually installed through bundled software without you knowing. You have to remove it immediately.