I've had an idea to upvote an answer when it's right and I like it, and downvote it whenever the answer is wrong. about questions I had the idea to upvote whenever I think that question might be useful to me too and downvote in cases that question is not releated to gamedev or has a very low quality. but there in many cases i've got both upvotes or downvotes based on the only term whether people liked answer/question or not? it seems not professional to me and I think our attitude toward quesiton answering should be changed to somewhat better, i'm not saying to adopt my idea but to have a better reason than just feelings.
The canonical meaning of upvotes and downvotes is probably best delineated by the hover text for the up and down arrows.
Up votes for questions
This question shows research effort; it is useful and clear
Down votes for questions
This question does not show any research effort; it is unclear or not useful
This answer is/is not useful.
The goal of voting is to help steer people on the site to do the right kind of behavior you think should be on the site by rewarding the user with points and by sorting their content to the top. It's obviously loose and subjective, but the idea is that with a certain critical mass of users it evens itself out in the end. Part of the idea is that the users on the site are hopefully "experts" who can just sort of look at a question and see whether it's good or bad.
As an aside, it is considered good form to leave a comment when you downvote (as otherwise the user doesn't know what they're doing wrong).
but there in many cases i've got both upvotes or downvotes based on the only term whether people liked answer/question or not?
How do you know that? It's not possible to say in general why you were upvoted or downvoted unless somebody tells you, so I think you might be overinterpreting some votes. Besides, even if that was the case, it's being done with the constraints of the system. That's part of the reason downvoting (for answers at least) costs, and why you can only downvote once.
it seems not professional to me and I think our attitude toward quesiton answering should be changed to somewhat better, i'm not saying to adopt my idea but to have a better reason than just feelings.
"Feelings" are not the best reason, but there are several good reasons that are relatively subjective. An answer may be poorly worded or other incomprehensible. It may have an explaination that is technically correct but suboptimal.
Avoiding subjectivity is basically impossible, so instead SE tries to amortize the negative impact of that subjectivity of the whole of its userbase on the assumption that the invested whole is more objective than the individual.