Graphics have gone mad...

Good afternoon.

Saving from Keynote or iMovie the screen resolution suddenly changed (Magnified) and I cannot fix it.

I have tried: 

Apple logo-system preferences-displays. 

1.Resolution - default for display

2.Scaled -  all 4 options

None work. Print squashed and screen shrinks.

I also tried the usual: 

cmd+option+P+R

Shift+Conrol+Op+power

Diagnostics

Nothing works.

Is the graphics card faulty?

Today on BBC news, only 2 words were shown on the screen. YouTube is impossible to navigate.

Some apps work, but display much larger.

Can you help please, as the Mac is quite hopeless at the moment. 

See 2 screenshots.

Thank you.