Try these, in order, to see if they fix your issue:
sudo ubuntu-drivers autoinstall- Using Synaptic, search for “nvidia” (without quotes). Toggle the “Installed version” column" to bring up just what you have installed. Post a screenshot of those results, here.
- Keep these for consideration, don’t try them yet until we have had a chance to look at your results from step #2 (in case step #1 doesn’t work):
a. https://askubuntu.com/questions/1208354/ubuntu-18-04-4-uses-llvmpipe-instead-of-intel-radeon-hd-8750m#1209318
b. https://forums.developer.nvidia.com/t/ubuntu-18-04-still-uses-llvmpipe-driver/82126/12