Bra comes from French brave same origin as bravo!, it has only one form; Bra. In all gender and number. It means respectable, proper, sth good enough, sth that's good for sth, and as an adverb it means rather/pretty, adequate
God. Bedre. Best. Beste. God. Godt. Gode. It's an old Norse word, hence the multiple terms and forms, old genitives, noun. This entry has 14 notes (and the first one has an additional 8 bullets) in the online dictionary of http://www.nob-ordbok.uio.no There is an awful amount of idiomatic expression containing some form of it. Stuff that's good, well off, nice. God is mostly better than bra.
Det var en god/bra middag. God means dinner tasted good, bra says sth about the performance/the event of the dinner. Du ser godt ut = You look nice and healthy (a compliment very well suited for someone who's been through an ordeal. Or just a compliment for anyone who shines and you can't figure out exactly what it is). Jeg har bra med penger. I'm well off (financially). Jeg er bra sliten. I'm pretty exhausted. Et bedre måltid. A better meal (ie better than most meals). Gode, gamle dager. Good old days. Er det godt for deg? Does that feel good? Er dette bra for deg? Is this good for you? Det er bra nok. It's well enough. Det er godt nok. It's good enough. De er mine beste venner. They are my best friends. De er ikke bra nok for deg. They are not good enough for you.
In English, "good" would be an adjective here, describing "food." Is "bra" also an adjective form of "good" in Norwegian or is "bra" acting as an adverb here describing how it "is?" (I always thought of "god" as "good" and "bra" as "well." Is this wrong? If so, when do you use each?)