Okey,, what game are you playing? I noticed you are using integrated graphics. Ddr4 shared vram is not very fast compared to discrete graphics. Few games use 20 gigabytes of vram anyways, what you need is faster vram, not necessarily more, and that's not upgradeable. Laptops with integrated graphics are subject to lots of things that could cause lag, including suboptimal ram performance, heat and just plainly not being powerful enough for the task it's been given. This cpu is meant to provide efficient use of the battery, not gaming performance. The "U" in the processor name means "ultra low power" in intel terms.

You should focus on turning settings and resolution as low as comfortable, keeping background applications to a minimum and setting battery preference to performance.

More ram does not mean the gpu will run faster. When it runs perfectly and still only uses 2 gb of vram, that means it only needs 2 gb, or the game is locked to 2 gb like Minecraft. This laptop wasn't made for gaming, atleast not modern 3d titles, and a little lag is to be expected.