Boris Pfeiffer 
The Three ???, Dino Danger (drei Fragezeichen) [EPUB ebook] 

There are strange things going on in the Dino-Park: Are the dinosaur skeletons really coming alive at night? Are they actually threatening the park owner? The Three ??? take on the case and stumble into a real prehistoric adventure!
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.