Complexity - I mean let's face it. Since Bitcoin and it's technology is just a new invention, people are having a hard time understanding it even only just the basics of it. The solution? Constant learning.
It being used for scams - People around the world have been using Bitcoin to scam newbie investors, and as a result, investors especially those new ones are having a hard time to decide whether they will invest into it or not. Solution? Proper teaching.
Storing - Nowadays, there are lots of hacks happening around the crypto space, and because of that, investors are having a hard time picking which wallet they will put their holdings on that is also less prone to hacks. Solution? The internet.
High Transaction fee - Just a few weeks ago, we've seen Bitcoin's transaction fee went to as high as 20$, and because of that, there are many who prefer to just hold their Bitcoins instead of selling it. The good thing though is that, the fees are already at it's normal (below 1$). The solution? I guess wait for the fees to go down then transfer your Bitcoins.

I guess it's good for the OP to ask so many questions here with regards to Bitcoin, and the basics of it. I mean you're also the one who posted that "Convincing" thing where you want to gave us one reason to convince you to buy Bitcoin. All of the challenges that I shared have one common solution, and that is learning. Learning even only the basics will help you a lot already.