Deleting value from dictionary.

[buran]

All keys and values are strings in this case.

So like:
dictionary = {"hello":["hey", "dinosaur", "dragon"], "fire:["volcano", "explosion", "boom"]}

well, note that your statement and your example contradict to each other. In your example the key is a string, the value is a list. And that list has number of elements that are strings.
anyway, something like this should work:

dictionary = {"hello":["hey", "dinosaur", "dragon"], "fire":["volcano", "explosion", "boom"]}
new_dict = dict()
for key, value in dictionary.items():
    new_dict[key] = [s for s in value if len(s)>5]
print(new_dict)