I have a friend that said I could have his Nvida GeForce GTX 1060 6GB card, would that be a real bottleneck problem for my system?
In games? Perhaps. In office use? No.
GTX 1060 6GB is good GPU for 1080p gaming, with ~60 FPS with high/ultra graphical settings. But since you do not game and use your PC as office PC (M$ Excel), GPU won't be taxed at it's limits, as it would be while gaming. So, it should work just fine.
Though, for office use with multiple monitors, look towards Nvidia Quadro or AMD Radeon Pro (FirePro) GPUs instead. Since those are designed and build for workstation use, including running multiple monitors at the same time. While Nvidia GeForce and AMD Radeon GPUs are designed and built for gaming use.
In a nutshell:
GeForce/Radeon - jack of all trades, master of one (gaming).
Quadro/Radeon Pro (FirePro) - jack of all trades, master of all but one (everything else, except gaming).