Using your same logic....<quoted text>
Not familiar with Islam.
If a teaching is correct, and you don't follow it and get a bad result, is it the fault of the teacher or the student?
If I ignore the Pythagorean Theorem and blow a Math test as a result, is the theorem wrong? No.
If you only believe in less than half of what Jesus taught, then you would be only a "half" of a follower.
Why don't you beleive Jesus?