I think they use an extension so check for that by clicking the '3 dots' (top right of the browser) then 'settings' then click 'extensions' (look on the left side). Click 'Remove' on any extensions you don't recognize.
The other way is using the notifications part of Chrome. To check that do the same clicks...'3 dots' ...'settings...this time click 'Privacy & Security' then 'Site Settings' (near the middle of the page). Check out the permissions under 'Recent Activity' and start blocking any websites you don't want.