~~ Is Bitcoin more convenient to use?
Yes.
~~ Is Bitcoin cheaper to use and where will that solve problems?
Online.
~~ Is Bitcoin safer to use than traditional payment options? Where will it be safer to use?
Yes, online.
~~ Is Bitcoin easy to use (How can we make it easier to use?)
Improve the help section of the wallet so new comers understand it.
~~ Is Bitcoin faster than other payment options? (Where can we apply it to solve problems with other slow payment options?)
Yes, in things like wire transfer or online payment.
~~ Are we using Bitcoin for the correct applications? (Trading or Currency) What should we focus on?
Currency. You can always trade your currencies (ie. forex), but that is besides the point.
There are some issues regarding "instant" use in physical situations (the infamous pay for coffee use case), which is what LN is attempting to address. The success of this idea will largely depend on the wallets implementing it. But for most common uses, the way traditional bitcoin is, is quite good enough.
If it were me, i would default the wallets to 1 sat/B tx fees. And optionally add some button or setting in case the user rarely needs the transfer to process "fast" (and with RBF you can always do that after the initial broadcast, ie. later). If you honestly and seriously analyze your online transactions, most can easily wait a day or two. I know some traditional methods involving bank wire transfer can take longer than that and merchants usually wait until that is cleared before shipping. Compared to that Bitcoin is instant. And most of the time, 1 Sat/B transactions get confirmed within an hour or two... At some point they will allow 0.1 sat/B, when that comes i would switch wallets defaults to it.
I don't like the wallets that try to guess network traffic and pick a fee that would "probably" get confirmed within a block or three. Some at least give you the option to manually input your tx fee, which to me, should always be the smallest non zero value. Especially after LN comes in widespread use for the "instant coffee payment" scenario.
This is to debunk the myth that "Bitcoin transactions are too expensive", no they are not, you just didn't set the proper fee, silly. If you are tipping someone some satoshis, you DON'T want your wallet picking a fee for you...