I already follow some tips like, trying to find the extensions, but when I open it there's nothing in it. Also my search also already Google, so I'm confused right now.
You set this in Safari* Preferences - you don't need an extension to do this.
In Safari, go to the Search tab in Safari → Preferences (or press ⌘ Command,)
* Safari 11.1.2 was used at the time of submitting this answer
There are actually two places to set search preferences in Safari. One is the Safari Preferences > General as discussed in @Allan's answer.
The other is presented by opening a blank window (no URL in the address bar), and clicking on the magnifying glass icon to the left of the address bar. Whatever search engine is chosen in this method will override the Preferences setting. See this Apple:SE Q-and-A for more information.
there may be several things happening
- Test wether it happens in safe mode .
Boot your mac in safe mode, and search something in safari and see if that fixes the problem.
- Make sure that your search engine is google.
on safari you can go to safari>preferences>search (see Allan's response) and on chrome you can go to preferences search engines. If Google doesn't show up under the search engines, or the search gets redirected to Yahoo, your computer may have an app changing this.
- Remove extensions.
Some extensions can change what your search engine goes to. If you have any extensions disable them, one at a time. Then try a simple search to see if that fixed the problem
- Other Options
if none of the above work out, your computer may be infected with malware. First, check through all of your apps to see if any of them could be malware. Then, install/run an antivirus/antimalware app to get rid of the malware