Many people have given you great advice regarding accuracy in cutting and sewing. In order to ensure good seam alignment, I pin the intersections using very skinny pins. Also, try to let your feed dogs on your machine feed your fabric. I have stretched blocks by pulling my fabric. You might find it helpful to check out the quilting classes on Craftsy. Some of them are free. By the way, my first quilts were not perfect, but they are still worthy in my eyes. Just like everything else, practice makes perfect.