OK great, that sounds pretty good for your saddle height then! Easiest way to change your riding position from there is with your stem and handlebars, I wouldn’t mess with the fork itself.
If you want to be more upright you can try a stem that’s shorter and has some rise to it, to bring the bars higher and closer to you. There’s all kinds of different handlebars that have rise to raise your riding position as well. Bike shop can advise on that if it’s something you aren’t comfortable doing yourself.
But to be honest 45° is a fine angle, so unless you’re finding it really uncomfortable or it’s hurting your hands or wrists, I’d say your bike fit is probably OK!
15kmh ain’t nothing to sneeze at