Date format

I took a SAMPLE CODE (for Connected scatterplot) from the R gallery
and applied to MY DATA, but got:
"Don't know how to automatically pick scale for object ..."
P.S. 1) R ver. 4.0 (Yes, Jeff);  2) Attached: mydata_dput (1 ??)

SAMPLE CODE
library(ggplot2)
library(dplyr)
library(hrbrthemes)
data <- read.table("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/3_TwoNumOrdered.csv
", header=T)

data$date <- as.Date(data$date)

# Plot
data %>%
   tail(10) %>%
   ggplot( aes(x=date, y=value)) +
     geom_line( color="grey") +
     geom_point(shape=21, color="black", fill="#69b3a2", size=6) +
     theme_ipsum() +
     ggtitle("Evolution of bitcoin price")

======
MY DATA
mydata <- read.table("E:/mydata.csv", header=TRUE, sep=";", dec=",")

str(mydata)
'data.frame': 7 obs. of  2 variables:
  $ date : chr  "01.01.2000" "02.01.2000" ...
  $ value: int  11 12 ...

mydata$date <- as.Date(mydata$date, "%d.%m.%Y")

str(mydata$date)
Date[1:7], format: "2000-01-01"

# Bert, thanks for the explanation!
# Rainer, thanks for the specific code!

# And then the problem:
mydata %>%
     tail(10) %>%
     ggplot( aes(x=mydata, y=value)) +
     geom_line( color="grey") +
     geom_point(shape=21, color="black", fill="#69b3a2", size=6) +
     theme_ipsum() +
     ggtitle("Evolution")

"Don't know how to automatically pick scale for object of type
data.frame. Defaulting to continuous.
Error: Aesthetics must be either length 1 or the same as the data (7): x"