Ulf Blanck 
The Three ???, High Noon in Rocky Beach (drei Fragezeichen) [EPUB ebook] 

Rocky Beach takes part in a competition to be part of a Wild West movie. The Three ??? and Uncle Titus are excited and help turning the small coastal town into a real Wild West town – with saloons, horses and coaches. Even Justus, Peter and Bob look like cowboys themselves. But unfortunately, there are villains in the Wild West, too. Can the Three ??? stop them?
In Rocky Beach, California, live the three detectives: Justus Jonas, Peter Shaw and Bob Andrews. Together, they are The Three ??? and there is nothing they don’t take on!
The three friends witness exciting detective stories, solve puzzles no matter how tricky, and can always rely on each other.