1. Run your game once to create default config.
2. Go to your Steam folder, then find the following path <Steam-folder>\userdata\<user-id>\1792250\local\SeriousSamSM.ini
3. Open the game config file, find the following commands inside and change them as following

sim_fWorldPrecachingStreamingLoadingDoneThreshold = -1;
texs_ctMaxUnloadsPerFrame = -1;
texs_ctTooMuchLoadingTextures = -1;
texs_fTooMuchToLoadAtOnceMB = -1;

Then save the file and start your game as normal.

Optional:
1.Try Vulkan graphics API in settings
2. In game go to Graphics options->performance->GPU Speed and set ground update speed to low.
3. In Task manager, right click on SeriousSamSM. Press go to details. Rightclick again and set priority to High.


I will not be answering questions, this is copy and pasted from this serious sam 4 post: https://steamhost.cn/steamcommunity_com/app/257420/discussions/0/3193615617164700752/