Hi, could you please edit out of your question the / at the bottom of the question. Thanks.

There are programs that switch default Google to you Yahoo search. Have you installed anything just before this happened as some programs carry a extra payload to make this happen with out your permission. ??

Please use more than 1 scanner as each uses diff tech :

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Save your Report and google each before deleting anything as do not want to delete something you need, If need help :

• https://forums.malwarebytes.com/topic/9573-im-infected-what-do-i-do-now/

Post in only 1 forum, then wait.

Please let us know if this solved your issue or if need further assistance.

You have this extension Search Web 1.0.18.404 it is probably the cause of your issue. The Malware scan should pick it up and remove it but please check Programs and Features to see if you can uninstall it first then run the scan.