Encrypt/ decrypt

Write a python code by

Using a dictionary, make a text encrypter/decrypter.

In decrypt mode, if the user inputs Y r u l8?, the program should output Why are you late?, for example.

In encrypt mode, if the user inputs See you later, it should output c u l8r.

Obviously you cant handle every possible phrase, but add as many as you can. Dont bother with multiword shortcuts for now (LOL, BRB, etc.)

How would this work?