From the Release Notes:
Dominate the GT4 competition at Brands Hatch and Hockenheim!
First chance to start: Monday, 27 January 2020
Last chance to start: Wednesday, 12 February 2020
Rewards: 2018 BMW M4 GT4, 60 Gold, R$100,000
Maximum Required PR: 63.7
And the usual excellent info from RR3 Trackside shows you will need all 3s upgrades to finish :
You can see details of the (already existing) GT4 Motorsports series here: