J.VERMen's Oxford Shirt Solid Casual Button Down Collar Shirts Long Sleeve Dress Shirts with Pocket

I wear a 17.5" neck and 34" sleeve length. What size do I need in this shirt?

Why does the 4xl white shirt fit perfectly and the navy blue fits too snug in the shoulders.

What are the measurements. For the large?

The sizes in the table do not seem to make any sense. The waist and chest sizes are so big compared to the length. Are these for obese people only?