Watch your language !
This is a all ages open webboard.
And for your information, avast doesn't install "some kind of browser".
The only browsers avast can install (depending on your settings) are the SafeZone Browser and Chrome.
Also Yandex is not malware.
Yandex is a Russian multinational technology company specializing in Internet-related services and products. Yandex operates the largest search engine in Russia with about 65% market share in that country.
If you want help, change your language use/mentality and provide details.