R seems to be treating all of my values in a column as seperate coefficients instead of seeing them as numbers to analyze. When using a regression, it hence conducts a multiple linear regression instead of a single linear regression. How can I overcome this problem? :

Data set:

To import the csv file, I've used the following code:
data <- read.csv("./path.csv", header = TRUE, sep = ";",stringsAsFactors = FALSE)