It's not uncommon to find yourself in that situation. Firstly though you need to recognise that you really get out of uni and your course what you put in. If you are just passively waiting for opportunities to offer themselves up to you to go out, meet people, make friends etc, then you probably are going to end up spending a long time waiting and a bit lonely. You really do just need to make a point of joining societies, going to the events and meetings for them regularly, regularly going out of your way to talk to other people on your course, in your flat and residence etc. That's the only way you're going to get anywhere with the social life side of things, at any uni.
In terms of the course it does also hold true that you get out what you put in, and you do need to remember that at uni it's really on you as the learner to go out and engage with the course. Lectures normally just cover the minimally examinable components (if even that far) and you're expected to go out and do independent study to engage with the subject area and topics more broadly and deeply. The lectures are normally just a starting point and/or a platform to go through examples together.
Of course it isn't uncommon for people to find that a given course at degree level isn't what they expected (or even what they like) due to significant differences in style and content from the A-level. Some notable examples I can think of include maths, physics, and economics (the former being a very different type of maths to A-level, the latter two being much more mathematical than the A-level usually). Languages can also be somewhat different I gather with a much larger emphasis on grammar. I've no idea what course you're doing or how you're finding it different from A-level, but you need to think about, for yourself, whether it's something you are OK with but just need to adapt to, or if t's just fundamentally not something you want to be doing at degree level (in which case I recommend seeing if you can withdraw and then reapply during a gap year - it might be early enough still that if you withdraw you don't have any fee liability!).