Ok so about 2 weeks ago i had a longer trip to do in my car (about 60 miles or 100 km's) and when i came off the highway and lifted my foot off the accelerator i noticed my foot was just numb, little feeling if any at all. however this is not the point, the point is, there are quite annoying vibrations in my footwell at higher speeds ( 50 mph+).

Upon arriving I turned off my radio and let the engine idle, this sounded more crude than it normally would so i opened the bonnet and looked at what the cause of the vibrations could be. turns out, the black box that lays upon the engine is really moving alot and is the culprit here in my opinion.
i checked again today and the vibrating has somewhat gotten worse.
Is there any way of tightening screws on this or not?

thanks in advance

Well at the risk of sounding too obvious, you would have to have a closer inspection of the box. Take the thing apart & use your loaf/judgement & ascertain what can be tightened or not.