Why does Yu-Gi-Oh and Master Duel plays different?

As a person who plays Yu-Gi-Oh master duel I decided to go to a place where I play Yu-Gi-Oh in person and boy that didn't turned out well cause I got cooked but I learned how to play in person more, it's just way more complicated with newer cards. My opponent decided to go easy on me and use a Skull servant deck while I use Odd-eyes, and guess what? He still beat me. Lol

He also taught me how the skull servant deck works. He gave me advice not to go to tournaments because I'll get cooked, so I thought why not play Yu-Gi-Oh in person more to get more accustomed to it and play it the right way.