Need help in Pronunciation!

Hi, I'm new to this forum and to Japanese, too. And please excuse my bad English ^^.

Could you please show me how to pronounce "s" and "sh" in Japanese, for instance, is "su" and "shu" pronounced differently? Also I have the same question with "z" and "j".

In addition, does "r" have 1 or more ways of pronunciation?

Thank you all in advance

Romaji is used to transcribe Japanese words into alphabets. "S" is for sa-column or さしすせそ, whereas "sh" is for youon or しゃしゅしょ. That's quite the same as "z vs j" or "ざじずぜぞ vs じゃじゅじょ." Thus, they have completely different pronunciation except i-lines "si/shi" and "zi/ji". (They are both for し, じ, respectively.)

Romanization of Japanese - Wikipedia