I'm doing good at it so far, right?
good! (colloquially) could also be written as:
I'm doing well at it so far, right?
Up 'til now I'm doing good, right?
So far I'm going good, right?
No problems yet, right?
-all have pretty much the same meaning.
I'm deeply offended by what he said about me.
-good! that is the most natural way to say that imo.
I haven't thought of that in a long time. (a memory etc.)
-good! Could also be said as:
I haven't thought about that in a long time.
Its been a long time since I've thought about that.
That takes me back.
I've never even doubted your talent for one second.
-good! Could also be written as:
I've never doubted your talent for a second.
And, can I use these interchangeably?
(lifting something etc.)
I was stronger than I thought of myself to be.
I was more powerful than I thought of myself to be.
-good! although power usually pertains to destructive forces (imo) so stronger would be the more correct sentence.
Could also be written as:
I was stronger than I thought!
I'm stronger than I thought!
Hope it helps! :-)