If you don't switch to Proton 3.16-9 you will need to change the ingame-"available memory"-option to "low". This however also leads to barely readable low-res-textures for documents and therefore I highly recommend switching to this older version of Proton. You can switch to Proton 3.16-9 by right-clicking on the game in your Steam-library, selecting "Properties", selecting "Compatibility", checking "Force the use of a specific Steam Play compatibility tool" and selecting "Proton 3.16-9".