Running a query in R after establishing dbconnect
I understand your question as: I try to send this query to the database but it doesn't work.
As far as I can see the trouble is here:

"select id as ID,
       date_c."Professional_Status" as 


You first start with double quotes and R thinks that the string ends at the next double quotes, so before Professional_Status. Use either single quotes like you do in date = '2018-01-19'
Or use single quotes at the ends and double in between. Don't mix and match, it will not work. 
Since Profesional status is not defined variable nor is it a valid R statement this will fail. 

Some small tips:
If you want to substitute professional_status with a variable you have defined in your R session, use something like paste("text", variable " text") or use the excellent glue package that allows you to write glue("text {variable} text") 
A final tip, if you use an IDE, like for instance RStudio, you can actually see that the text ends at the first second quote, because the highlighting is different.