Gta V running poorly on 4gb of ram is a common issue. 8gb is the min i reccomend for that game. However I can't tell you if that will definitely fix the issue with out knowing what gpu you have, only posting how much vram it has tells me very little about its performance.
MERGED QUESTION Question from Alvi_2 : "My gta V is working too bad!"
my laptop has intel(R) Graphics 4600 2gb and the processor is intel core i5-4200m firstname.lastname@example.org. and 4 gb of ram will it work after additional installation of 4 gb ram or not.
Else is it a problem of the processor?!!
Upgrading to 8gb won't help much, your gpu is just too weak and actually has 0Gb of dedicated vram all of its vram is shared from the system ram(upto 2gb). So even with 8gb of ram the game is still going to run poorly. Being a laptop there is nothing you can do to make it run better as the gpu is not upgradable on your laptop.