Hi and welcome!!!
There are no concrete rules in what order to assemble parts, just do step by step and hope for the best
After a while you learn what works best and I often only use the instructions as a guide on how it "could" be assembled, but not necessarily in that order.
Also the quality of instructions differs a lot between different manufacturers so some are super easy whereas others are almost useless. Most modern kits have good instructions.
The same goes for painting. Tanks and other armour you can often build almost the whole kit before you start the painting process whereas with planes you have to paint something in almost every step. It gets more obvious with experience but we all still miss painting something and have to backtrack and use a lot of masking...
Boats and ships I've got no experience with.
Read the whole instructions first and make a plan on paper. That helps a lot!