"Than" is to contrast something. So I would say "I liked Big Hero 6 a lot more than Frozen." (This statement means nothing :D) But "Then" is to place a time. I would say "I remember how I used to ride my bike to school, and then sometimes I would forget about that crack in my road, so I would almost break my bike riding over it." (Again, that phrase means nothing) So there's a pretty big difference between Then and Than. :D I hope I helped.
Then refers to a sequence of two or more events. i.e.- The professor handed out a test then, took it up to grade. Than refers to quantity. i.e.- I have a higher grade than Bradford.
