If you load an older save, if available, does everything work properly? If not try creating a new profile and start a new game on Story difficulty to test.
If a new game in a new profile also has the same issues:
Try creating a new Windows administrator user account (either with the My Documents folder in the default location, or on a different drive, if available), switch to that account and try starting the game from there, directly from the '..\SteamApps\common\Divinity Original Sin 2\DefEd\bin\EoCApp.exe' executable.
Try doing a clean boot and then test the game. Click Start, or hit WinKey-R, type in msconfig and hit enter; in the General tab, click Selective Startup, uncheck Load startup items (if required) and leave Load system services and Use original boot configuration options checked. Next, click on the Services tab, check the box to Hide all Microsoft services, then click the Disable All button (maybe make a note of which are currently enabled/disabled), then click OK and reboot the computer.
Run msconfig again to switch back to the normal boot configuration.
If a new game is fine but recent saves have these issues, please email supportdos2@larian.com with your latest save (or a Dropbox or Google drive link, etc), and if older saves are ok, the most recent save that is fine, and the oldest that is not. If you are using any non-Larian mods, also include a list of those enabled and/or the modsettings.lsx file from your profile folder.
Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin 2 Definitive Edition\PlayerProfiles\<ProfileName>\Savegames\Story' folder.
In Windows Explorer you can zip a file or folder by right clicking on it/them and selecting 'Send To | Compressed (zipped) Folder'.