It's not because you're new that the bias edge is giving you trouble. The bias is tricky for experienced sewers too. When ever possible I sew the bias edge of triangles from two squares put together. This won't work for your situation because you are trying to sew them into an existing pattern. Just sewing them in has probably stretched them. You may need to start with new fabric. If you are doing flying geese, I use the pattern where you start with a rectangle and place a square at one end. You sew the diagonal and then trim the extra fabric at the 1/4 inch seam and repeat on the second side.