Kornelia S. answered 5d
I offer my knowledge and experience to fit your German learning needs.
The correct translation for: "The apple that I'm eating is tasty."
"Der Apfel den ich esse ist lecker."
When using the sharp ß it is used as a conjunction and a word that connects words, phrases, or clauses to form a sentence.
The ß is used when the preceding vowel (including Umlaute) is long: Fuß (foot)/fu:s/.
The ß is used after a diphthong (i.e. a double vowel combination such as "ie", "ei", or "au"):
beißen (bite)/baisn/
draußen (outside)/drausn/
Note: After a short vowel, a double "s" is used instead of the ß:
Nuss (nut)/nos/, or essen (eating/eat)/esn/.
I hope this helps.