can not install packagers in Rstudio(files missing in /usr/lib/R/etc)

I installed the R 4.3.3 version on my Ubuntu 22.04，but for some reason it didn't work, so I had to install an older version. I purged the newer version and install the 3.6.3 version with another rstudio, but it won't open.

It says this:

R shared library (/usr/local/lib/R/lib/libR.so) not found. If this is a custom build of R, was it built with the --enable-R-shlib option?

I deleted the source dir again and uninstalled rstudio, then installed the new version again (I am just a beginner). . .

Here's the point, when I open the R, it says

/usr/bin/R: line 249: /usr/lib/R/etc/ldpaths: No such file or directory

"on the top,and "uring startup - Warning message:

In file(file, "rt") :cannot open file '/usr/lib/R/etc/repositories': No such file or directory 

And when I try to install packages in studio, parts of the errors are like

cannot open file '/usr/lib/R/etc/Makeconf': No such file or directory

And:

Warning in install.packages :installation of package ‘data.table’ had non-zero exit status""installation of package ‘htmltools’ had non-zero exit status/usr/lib/R/bin/R: line 142: /usr/lib/R/etc/ldpaths: No such file or directory/usr/lib/R/bin/R: line 249: /usr/lib/R/etc/ldpaths: No such file or directoryError in file(con, "r") : cannot open the connection"

The files in my /usr/lib/R/etc are like in the screenshot as follows, the repositories file was created by my self and it is empty: