Are we forced to purchase bonus skills?
I've been having so much trouble with adverbs that I've had to start buying hearts--and several times so far today I haven't gotten the heart I bought, though my lingot total has gone down. So now I have one unfinished section which I feel I will need every one of my lingots for, and the next untried section is a bonus skill requiring 20 lingots which I can't afford. Two days ago I was allowed to move on to a new section, and then go back to my troublesome adverbs section, of which I can only take so much per day. But now it looks like I will be required to buy the bonus section, which I can't afford, and can't choose any other untried section but that one. ??
You can only work on lessons on the same level at the same time.
This means that you can work on Adverbs and Objects at the same time, but you must complete both before you can move on to To Be, Places and People. Once you get past you current level (Adverbs and Objects) you can work on the next three skills (To Be, Places, People) in any order, but must complete those three before moving to the next level.
You don't have to buy Flirting to advance, but you must complete Adverbs before you can move to the next level of the tree.
The bonus skills (in your case flirting) are purely optional and supposed to be for fun. It also seems that you will have to finish the adverbs before you move on to the next level.