Now this is a strange one.
finally think ive found how to fix it, but not entirely sure what caused it.
firstly, make a backup of your project folder, just in case.
make sure Godot Editor is Closed and not just minimised for the next part.
go into your project folder in windows
then delete the .godot folder shown below.
reopen Godot Editor and open your project.
this folder will recompile and that error should be gone.
but I see you are left with two other parse errors.
to get rid of these.
need to ensure that where you have viewport_size on lines 8 and 9.
these have to have a capital V at the start, to match the variable your declaring on line 5
hopefully that sorts the couple of errors out, ill keep digging to see if i can find out what the actual cause was
Darren