Staking is just put your money on certain thing to hope to get interest and forget it for next few years. If you are looking for "big" income with staking coins then it's a misleading idea and not for that type of benefit. But, just for some side income that you don't even bother to check it time by time then it would be a great idea to stake some of dogecoins of yours.

Assuming I've made up my mind to hold on to a token for many years but after a year this token hit a new ATH what should I do as a newbie? Sell or not sell?

One of the reasons why traders loose money everyday in their trading is 'greed'. A trader will hear about a particular coins he wouldn't even do research or proper findings to know the future of the coins which he wants to trade his money on but rather the greed in the trader will push him to use all he has with the aim of making 4 or 5 times of his trading capital.
Traders are big risk takers so everyone should know what he or she is trading on so that when you loose which is normal, you will learn more.
No trader is perfect but mastering coins you trade on can help you, remember trading is like a gamble you either gain or loose.
Do not trade with everything you have,your egg can not be save in one basket, I have lost but I have gained more in trading with the help of research and mentorship programs.

There is a huge competition between cryptocurrencies, many believe just dynamic and self fulfilling ideas with different properties and a variety of incentives may survive! Others expect fiat money will leave behind reliance on quantitative competition!

I think cryptocurrencies are not able to defeat fiat currencies without changing nations culture and ethics! what do you think?

Guys, any suggestions for short-term investment?