Question Laggy gameplay, PC randomly black screens/restarts on its own

Jan 1, 2020
Basically, I received the graphics card (Asus Rog Strix RX 5700 XT) on the 30th of December, 2020, after a brand new purchase from Previously I had a gtx 1060 3gb installed so I used DDU(Display Drivers Uninstaller) to delete my Nvidia drivers and uninstalled the old card and installed my new Rx 5700 XT, downloading the drivers also. Now my pc is booting up slower, programs take longer to boot up and worst of all, my games graphics are really laggy, even though I have very high fps. As well as that, my pc has been restarting on its own as well as the fact that I've been getting black screens on my main monitor, forcing me to shut down and reboot the whole computer. I researched and saw that the power supply could be the fault but it is in working order with over 200 watts of unused energy being used on it. Please get back to me as soon as possible as to how I may fix this issue.

Please help diagnose this issue if u can :)

(PC List)
R5 3600
Asus ROG Strix RX 5700 XT
Corsair Vengeance RGB PRO 3200 MHz
CoolerMaster Hyper 212 RGB Pro
MSI B450m Mortar Max
EVGA 650watt gq Gold 80 Plus Certified
Sabrent Rocket 512gb NVMe m.2 SSD
Seagate Barracuda 2tb HDD 7200rpm 256mb cache
Seagate 1 tb external hdd