My pronunciation challeanges and goals

     I underlined thirty, works, marketing firm, river, bridge, and called. Every word has /r/sound except called.
And when I said rise, clash, sheet, won't, though, measure, shin, born they were not accurate I think.
I need to distinguish /s/, /sh/, /z/ 
    So, my goal is to pronuce /r/ sound accurately and to distinguish /s/, /sh/, /z/.
And to be more natural I need to practice more.
    It was a big challenge for me to pronuce vowels, either.
After learning about vowel sounds I will update more about that.