Normally the game reads automatically the correct maximum texture graphic memory.
Sometimes it may happen that the graphic card driver sends the wrong data causing a malfunction.

To solve it, please start your Launcher and click on the „Options“ tab.
– On the top you see the field „Renderer Type“, here you can manually change the memory usage by changing the value in the „GPU/RAM“ Dropdown Window (on the very right).
– Choose a value which has a star next to it and start with trying a high value (test it if it works, if not, go back and choose a lower value, etc)