I read somewhere that there are 5 acts with 5 chapters each. I just beat 3-4 and it took me straight to 4-1 am i missing parts? Id really like to play as much of this game as i can

I don't think it is possible to skip chapters in this game. Who ever told you each act has 5 chapters was probably wrong. It's been awhile since I played it but the only way you'd be skipping chapters is by some glitch.

I could not be remembering right, but one chapter is very short..or something . I vaguely remember something being very brief.

You're not skipping anything. The first act has one chapter, the second and the third have four, the fourth has six and the fifth has five.