Returning to the hobby

Returning to the hobby after a 10 year break, it has changed so much. I use to use an external filter all them years ago and had good success.
This time I am using a sump and have not much idea how to proceed, so am studying you tube all the time. So am here for loads of advise. Please remember the only stupid question is the one you dont ask, so I'll be asking loads.
So thanks in advance for any advise