Vram is the memory on your graphics card the only way to increase that is to upgrade your GPU. But to be quite honest your HD 5770 should be able to handle the game very easily. See here. What are the rest of your specs? Motherboard,CPU, RAM, operating system, maybe something there.
Qualcomm Snapdragon 835 benchmarks: Antutu, Geekbench 4, GFXBench and PCMark results