¿Cuál es la diferencia entre de y del ?Puedes dar oraciones como ejemplo.

"Del" es una contracción de la preposición "de" y el artículo "el"
Un ejemplo:
"La comida del perro" which means the dog's food.
U could also say "La comida de el perro" but we don't, why? because it sounds a bit unnatural. So basically what we do is to put "de + el" together because it's easier to say. The same way you might use the apostrophe in English and say "they're" instead "they are".
"Flor de el cerezo" "estrella de el cielo" "payaso de el circo" "carta de el abogado" What do these sentences got in common? They all have masculine nouns ( el cerezo, el cielo, el payaso) and if you are trying to say "of the" or "from the" you have to place the preposition "of" (de) before the article "the" ("el" in this case) resulting "de el" and as I said it's just a way to fix it and make it "prettier" and easier to say :)
If it was a feminine noun you wouldn't have to do anything because it sounds just fine --> "La comida de la gata" "The (female) cat's food" Versus "La comida del gato" " The (male) cat's food"
Hope it gets a bit more clear for you.