Disaster !

I'd complain to roundup that it didn't kill the whole lot as intended.

 

Really bad luck. However get a packet of grass seed and scratch out the dead stuff. By the summer you'll then have some extra green designs in your grass to replace the brown ones! Could be a lot worse if it had been residual weed killer. Friend of mine had a truly lovely garden. Next door neighbours had their tennis court re-laid. Before the new surface was put down the contractors sprayed the court with what must have been the strongest weed killer known to man. That night it poured with rain and the weed killer washed onto my friend's garden. It killed EVERYTHING including a 40 year old Leylandii hedge and 2 huge (over 100 year old) Beech trees. My friend was absolutely heartbroken and to make things worse he wasn't able to do anything in his garden for 2 years while the weed killer remained active. Yes friend got £1000s compensation but he was a wealthy man and didn't need the money plus he was getting on in years. All the money in the world wasn't going to replace what he'd lost and he didn't have time left to see his garden looking mature again.

 

But you will have residew in the dead bits, and when the grass seed starts to come up it may kill the new growth

 

Glyphosate doesn't persist in that way (so that, at least :(, shouldn't be a problem)

 

Despite the new mysterious lawn rings (you can pretend aliens landed) your garden looks fantastic, I love the different areas. It'll come back quickly I'm sure