"Znám hodně dívek."

[openminded2]

Again, duolingo offers “mít” as if it was an English word option.

[VladaFu]

It chooses the words randomly. It can chose Swahili words if it wants... No need to report, we can't do anything anyway.

[ActiveBoredom89D]

What is the difference between 'mnoho' and 'hodne'?

[VladaFu]

To denote a quantity - mnoho is more formal than hodně.

As an adverb modifying some adjectives you can only use hodně in the same meaning as velmi: hodně velký=very big.