I see that the Celts have not wasted any time at all
Well, an already impossible situation became even worse. Although they are on an island, the close distance allows them to ship over way too many troops, for this phase of the game.
You could make peace in a few turns without losing any cities, but even then...
Anyway, if you still want to continue, block the coastal tiles with units so as their galleys are forced to travel bigger distances + use cats to injure the galleys (delays shipment of units). Also, in these cases, since the AI sets a destination point to land units on, it is possible by covering that tile to make their galleys go back and forth, at least until they change their destination point.
Btw, I have managed to load the last save, but unfortunately I keep experiencing the bug I described.
I reinstalled the game from Steam (my CD version will not run in W10

), and the game runs smoothly until I exit the game. If afterwards, I try to reload the game I get this:
and this:
So basically I need to reinstall every time I exit the game... If you guys have any suggestions on how to resolve this problem, let me know.