I am still unsure how to increase my speed. I have increased distances I can cycle- I can do long distances comfortably without getting tired but haven't improved my speed...

Endurance is there but not speed.
As many have said a change in groupset wont make any difference apart from your bank balance, theres lots of cyclists spending big money to buy speed in the vain hope of becoming faster cyclists by spending money. Best way to get faster on a bike is to start with a bike that fits you, second get it set up right for yourself and then start a training plan.
Best advice i can give about a training plan is to start and watch Veloharmony on utube or similar, either that or start and read up on it, but training really means every time you cycle theres a purpose and you stick to it should it be slow easy days, intervals cadence work whatever?
what i find with most cyclists wanting to get faster is they go to fast on there easy days and to slow on there hard days and end up never really getting any faster?