Acer V5-122 (AMD Radeon HD 8250): graphic drivers problem after upgrade to win10

Dear community,

After a short research in internet I need to ask I hope a simple question considering the graphic drivers on my Acer V5-122 (AMD Radeon HD 8250):

I used with win8 an external monitor for which I manually (in registry) defined some additional resolutions. After a while I decided to make additional changes considering screen quality (downsizing resolution and color depth). Unfortunately that caused an error which I didn't expect: the screen became split into two parts ¼ left as previously ok and ¾ on the right side with wrong dpi or color depth (I am not sure). I hoped that after upgrading to win10 and installing of new drivers (download from the acer.com) the screen error will disappear, but unfortunately I doesn't happen (see the uploaded image). Can someone suggest a workaround (maybe removing of the drivers and new installation or similar) which will provide that this small but effective notebook work again perfectly?