GST URD PURCHASE

sir,

please explain  if URD Service Purchase above  50000/- each Bill   Tax Applicable  how show in GST1/  OR GST 3B RCM Paid after how showing  for tax claim 

rent paid URD person  RCM calculation  tax rate  ?   supposes his  product dealing rate   below  5% Gst 

rent  18%  RCM Pay 

main product dealing rate 5% or below