As it was mention before, idle temps on Ryzen 3rd gen are around those values with most coolers (stock or avg aftermarket ones). As long as around those numbers you are fine.
What you should worry is load temps as Phaaze88 wrote.
For monitoring use either Ryzen Master or hwinfo 64. Pick 1 monitoring software and stick with it, don't run more than one at the same time.
For testng, you could try with CR 20 (you can set a "loop" time on the options, I usually put at least 10 mins - 600 seconds). For Ryzen 5 3600 in a decent case with decent airflow (and not soo hot weather) you may get up to 85~88°C after the 10 mins loop (with the stock cooler). Thats what I got on the two PCs I build with the R5 3600.
Game temps, as long as theres good airflow inside your case, should be below 80°C (unless you play some really heavy cpu game)
If you don't like those temps and/or the fact that you may be loosing performance cause of them (boost frecuency and voltage will get lower too to keep the temps from going higher and higher) then you may want to consider an aftermarket cooler.
The one I got in my signature is the lowest I would go (as long as it fits inside your case) to get a much better experience, temp and performance wise. Otherwise you can always pick a AIO liquid solution. Or even pick a much better air tower cooler.
Once again, if you pick the right one, the aftermarket cooler will help you lower the load temps, and should help you get a higher boost frecuency on all-cores works, but you will probably see the same idle temps going up and down, thats how the 3rd gen Ryzen works.