One gene form one polypeptide, not one protein. This was one of the syllabus dot point.
Gene (a segment of DNA) ---- transcrption ----> mRNA (with intron and exon)---- splicing ----> mRNA (with exon only) -----> translated in the ribosome ------> a chain of amino acid (a polypeptide)
this polypeptide can then be folded into its shape to form a protein by itself, or combine with other polypeptides to form a protein.
You need more detail than this flowchart, including how the condon (3 bases) code for one amino acids. tRNA etc.