This wont work if the x values dont coincide.
I suggest rounding the x numbers in the second series to nearest 0.5
Create a table of x values from 90.5 to end in 0.5 increments
LOOKUP table against first list to insert y value where they exist
and agains
LOOKUP table aginst second list to insert matching x values in seperate column and then against second list for matching y values
combine the two columns and plt those figures
I’ll have ago and see if that works