u/DebtChemical404

My brother gave me his pc before he went to the Air Force and it has worked well for a while now but new games are making it lag or not be able to play it. To be honest I don’t know a lot about building pcs but I want to learn so I was wondering what to upgrade first. The CPU is a AMD Ryzen 5 2400G with Radeon Vega Graphics and the GPU is a AMD Radeon RX Vega 11.