Uni is such a jump from school; I struggled a little in the transition from school to uni mainly because I was the first person to go so my parents didn't exactly have much advice to give. I'm in my final year now and I feel so much more adjusted. It will take time, but it is possible. I highly advise seeking out your academic advisor or social advisor to get tips on how to adjust, how much time you should spend studying, study tips and so on since the way you work with uni is miles apart from how you did it for A Levels. Believe me, most people struggle in the first year and I believe that's why it doesn't count towards your degree classification; it's your year to make mistakes, learn the ropes and so on so you can feel confident going into second year.
With friends, I think first it's best to try your roommates/people you live close to since you'll be seeing them more often. Just a quick hi in the morning, maybe see if they go out and tag along and see how that goes. I actually didn't make any proper friends until December of my first year since my roommates were party animals and only connected with the people I had my classes with. Societies are also great (as cheesy as it sounds) since even if you know no one there, you have that initial shared interest that you can talk about.
But yeah, I agree with the others. Don't let this initial bad experience turn you off uni. Some people can just come in, make a ton of friends and feel like home within a week, whilst others, like myself, needed time to properly settle in. I'd say wait until December and see how things have gone. If it's the course, you can usually change to another one in second year if the core modules are similar. I did have a friend who goes to Oxford who ended up taking a year off (he's going back in January I believe) simply because he was under so much stress and needed time to get back together. Consider taking a year out and pace yourself if that's what you need. I'm hesitant to say drop out and never go back since university is such an interesting experience as well as being advantageous in getting jobs, so I wouldn't want you to drop out and look back in a few years time regretting not going. But at the same time, if you continue to find yourself at odds with uni, then there is no shame in leaving. University isn't for everyone.