Honest, Honestly
adverb, noun, な adjective
You have correct and fix. When you're always fixing things to make them correct (for example, someone's lies!) you are a very honest person.
しょうじき
This is a jukugo word, which usually means on'yomi readings from the kanji. This is the case here too, but both kanji use their slightly less common secondary readings. You do know both of those, but in case you need a little help, here's a mnemonic anyway: Be completely honest, what's the strangest sound you've ever heard? The Shougun (しょう) going "jikijiki (じき)"?! Honestly, that does sound quite strange...
川田さんは、とても正直な人です。
Kawata is a very honest person.
正直に言って下さい。あなた、ニコラス・ケイジさんですよね？
Please be honest. You're Nicholas Cage, right?
正直、私は大人になっても一人でベッドに行けません。
To be honest, I'm an adult but I can't go to bed by myself.