You need to merge goals and assists into one column. You can do this with pivot_longer()
data <- data %>% pivot_longer(., cols = c(G, A)
This will give you two new columns of "name" and "value". So you will then want to change the column name of the new "name" column.
colnames(data)[3] <- "type"
Put whatever number column 'name' was in the brackets, I put a 3 in there as I think it will be column 3 but I am not certain.
Then you can plot by
ggplot(data, aes(x = as.factor(Name), y = value)) +
geom_bar(stat = 'identity', position = 'stack',
aes(fill = type))