You can pass back from Overleaf to Rstudio, that is, a tex file and work with Rstudio on a markdown file using pandoc but you will need to install pandoc on the machine or the server where you are working. So, you could use git to read the file from Overleaf back to your repository and then do something like:
pandoc from latex to markdown -o filename.Rmd filename.tex
You will get back the Rmd file (you can choose to override or save it with a new filename) and work on it using Rstudio, then export it back.
Let’s say you did not want to do this. In that case, as you cannot analyse any data on Overleaf (it only allows you to write text), you can continue to work on your Rmarkdown file, generate a new latex file and choose to merge the old and the new file to generate a new file containing changes in both files.