I don't see anything to upgrade wise off the bat.
I mean you can always change out the grips, pedals and saddle to what fits you but I think you just need to ride it for what it is. Thinking of a new fork already has me thinking you need to return this bike and get a bike in the $2000 range where it will come with a nicer fork and better brakes. Forks these days are $600-900, brakeset is another $250 with rotors.
Parts I'd change
Grips $15-25
Pedals $50-150
Saddles $50-150 if the stock seat doesn't feel right
Tires to match your trails $50 each
Riding knobby tires on the pavement for miles upon miles will wear them out a hint faster and has more resistance so you will be slower compared to some fat slick tires. But then you also lose that ability to ride to trails or go exploring if you see something cool on the side of the road.
__________________
Rule #10 // It never gets easier, you just go faster.