Can I RUN Fortnite at 4gb ram and i7??

Solution
depends on the usage of the game. If the game is throttled by other things, the GPU won´t have to work that hard. Other things could be RAM, hard drive, CPU, the game itself
Despite that it´s a laptop, adding another 4GB to have 8GB of RAM should be the best upgrade for your config.

Which laptop brand and model do you have? Should be labeled underneath it. Depending on which laptop you have, it´s DDR4-2400, LPDDR3-2133 or DDR3L-1600 you would need to upgrade.

But still, Fortnite will run on your current config.

Should run a bit better or equal to this one:
https://www.youtube.com/watch?v=TFjHRRL_l0g