I found them to be non intuitive especially Algebra (groups, rings, fields).
Well, there's a quite common misconception that intuition is something you have. Rather, intuition is something you develop when working on a subject; that's one of the reasons to have exercises, to develop intuition. Intuition is nothing than a set of (often unconscious or semi-conscious) heuristics.
Note that this point is not restricted to mathematics, but is true for anything. For someone who has never seen anything flying (be it a bird or an airplane), it would seem unintuitive that something can fly. Because we know such things, we have a pretty good intuition when objects can fly, even if we cannot do the aerodynamics to formally analyse the flight of a bird or an airplane.
You obtain intuition by working with the subject, by exploring simple cases, by exploring special cases, and by simple practice.
I found it hard to do proofs in assignments or write my own.
That's because you haven't yet developed the intuition for them.
Maybe my teachers screwed it up or I am not intelligent enough
I can't comment on whether your teachers screwed up (I didn't attend their classes, after all). But I don't think it is a lack of intelligence (your post indicates that you are able to clearly identify and formulate issues, which IMHO indicates that you should have the mental requisites for mathematics). It may, however, be a lack of self-confidence: If you assume you won't understand it anyway, you may not put sufficient effort into understanding, and as result your assumption can turn into a self-fulfilling prophecy.
If you think it may be because of your teachers, you might consider to find some course on YouTube (there's lots of material there) and see if that helps you.
Lots of things did not make much sense, especially Algebra
Then try to find out why the rules are that way. In particular, consider what they mean if you consider numbers; most rules get obvious when you consider numbers, and for those which don't work with numbers, finding out why they don't work with numbers will generally be instructive as well.