It is my first article ever in this field. I submited it to a high impact journal last year and just got the decision today -- acceptance with major revision. I have no idea whether this bad or not. One of reviewers sounds unreasonable while the other was asking relatively good questions. Can someone explain to me what to do, my co authors honestly did not believe in the idea of the paper and called it bullshit on multiple occassion .
Congratulations. If they give you major revision, you have to revise the paper thoroughly. While they are in their rights to reject the revision, this is now somewhat unlikely, unless, of course, you do not do the work on the revision. Pay attention to all the reviewers comments and suggestions. You usually have to provide an additional paper on how you addressed them.
There is a strange double message here.
First: acceptance with a major revision is a good thing. It's an acceptance.
In response to
One of reviewers sounds unreasonable while the other was asking relatively good questions.
you pay attention to both reveiwers. Read the "unreasonable" one's comments carefully. Put your prejudice aside and think about whether what they say is sometimes reasonable.
When you send your revision to the editor, explain which suggested changes you accepted, and which you rejected (and why).
my co authors honestly did not believe in the idea of the paper and called it bullshit on multiple occassion
is weird and raises several questions. Why did they think so? Why did they agree to submit that work? Might the unreasonable reviewer be right? Are they willing to work on the major revision?
Answers to those questions might affect your decision about what to do next.
First, it's concerning your co-authors didn't support the idea of the paper. It makes it sound like you wrote the paper alone.
As for your major revisions question, most papers require revisions after you submit it to a journal. Some papers require minor revisions (e.g. like graphs, tables, or grammatical fixes)
Major revisions refer to the claims you made in the paper. Meaning, your paper looks promising, but your claims are so big that you must support them more thoroughly.
For example, perhaps you made very big claims, but you didn't provide sufficient information/data/stats/equations to support your claims.