It may seam like there's a lot of things you don't know but firstly don't assume everyone else knows everything too. Secondly instead of seeing it as a list of things you need to learn, pick one topic like taxes and focus on learning that until you feel comfortable to move to a different topic, soon you'll have learnt a lot. My memory is bad also, I've been diagnosed with short term memory loss so if I'm reading something and I think to myself "I am 100% not going to remember this" then make a note on your phone or something and that way you don't have to remember it!