Die Hemden des Mannes sind groß.
I got this sentence in dative prepositions and i’m confused of “des” and “Mannes”. If anyone could give an explanation or a link that would be great!
"des Mannes" is the genitive case; it means that something belongs to someone.
Here's an explanation: https://www.dartmouth.edu/~deutsch/Grammatik/Nouns/genitive.html
And the different word forms of "der Mann": http://www.canoo.net/inflection/mann:N:M:er
So in your case, it is
The man's shirts = The shirts that belong to the man = Die Hemden des Mannes.
Well done Heike! That is the most straightforward and useful description of "Case"I have ever read. As an English speaker with a fairly rudimentary grasp of English grammar, "Falle" has haunted me since starting to learn German. I have always been amazed that small children in Germany are able to grasp it so quickly. Where it confuses me still after decades.