Correct any vitamin deficiencies, rather than take vitamins generally. The most likely is probably vitamin D deficiency. Indoor office worker in a northern latitude? Even if you do spend some time outside you are likely deficient during the winter.

And eating nutrient dense food is the best way to get vitamins.

Start with a healthy diet before you start taking vitamins. They are probably not necessary, unless you are already eating a perfectly healthy diet (which I doubt). I suppose it could be helpful if you refuse to eat healthier...

I completely agree with you on the sleep aspect. Sleep does wonders for concentration, creativity... I would also recommend a standing desk.

could you elaborate on the vitamins part please? I feel I need this but no idea what to get exactly.