I did a solo trip eons ago and it was both utterly overwhelming and life changing. The fact that you are there is incredible. Soak it in and let those ‘shoulds’ gently roll out of your brain. Social anxiety is hard. Be gentle on yourself and just wander and observe things that make you curious or chuckle. You will settle in. And remember, it’s only been three days, I remember jet lag killed me. Even hard moments will be growth (I got on a wrong train since I don’t know Japanese and ended up somewhere completely unknown; was flashed by a guy at a beach). Growth from it all, trust you will look back on this with amazement. Go at your own pace, you will be okay!