Imac problem

[Barmouth]

I have a mid 2010 imac (High Sierra).
When I put in a search on Chrome it always opens up on another site like BBC news or the National Lottery etc:
What is causing this?

Many thanks in anticipation

 

[velocityg4]

Run a scan with Malwarebytes, check extensions installed in Chrome and check the search settings in Chrome.

You only need the free version of Malwarebytes.