It's true — the German language actually has no translation for the adjective “fun” (as in “a fun time”, “it was fun” or “a fun person”). Sure, as a noun (e.g. “We had fun”) German has the word Spaß, and the adjective lustig (“funny”) comes close.
Yet to describe situations that are “fun” but not necessarily “funny”, German comes up short and the construction Spaß machen (lit. “to make fun”) needs to be used.
Achterbahn fahren hat total Spaß gemacht. Riding the roller coaster was totally fun!
Fallschirmspringen macht mir Spaß. Skydiving is fun for me.
More words that come close:
unterhaltsam / entertaining
amüsant / amusing
witzig / funny
vergnüglich / enjoyable
geil / awesome or wicked (very slangy)