Hi,
You can increase the RAM to 16GB (2 x 8GB) but you cannot change the graphics because it is a chip that is integrated onto the motherboard
Here’s a link to the [https://download.lenovo.com/consumer/mobiles_pub/lenovo_g_z_50_series_hmm.pdf|service manual]. that shows how -p.41
Here’s a link to the [https://pcsupport.lenovo.com/au/en/products/laptops-and-netbooks/lenovo-g-series-laptops/g50-80/parts/PD100418|specs]