This is a good question, especially as I feel your pain with coming from a non-object oriented languages…and I have actually have no good answer; the rule engine in OH2 uses a DSL (domain specific language) that is based on Xtend which in turn is based on Java; for both of the latter two, there is plenty (which in itself can be overwhelming) of help out there, but the “fun” starts in the “based on”, which means sometimes it is just so slightly different in OH2 that the general help does not work, does not apply, etc…you don’t need Java experience luckily (speaking from experience here) but some of the concepts and some very basic knowledge will help
Either way, the concepts of objects is critical. Some of the basics for object oriented languages are captured here, maybe this will help:
(one of the many great posts from Rich, he always adds great background and information…)
And of course regarding things, items and rules, this whole chapter here is a must read (and re-read) https://docs.openhab.org/configuration/index.html
VSCode https://docs.openhab.org/configuration/editors.html is a god-sent as it will check a lot of syntax for you and more importantly, give you an idea about all the methods that can be applied to the object of interest…this alone can help a lot…and provide search terms that help further…
Your specific question regarding now… statements may be one of the more difficult topics, see my earlier comment; and in addition, as this is your heating, you may want to consider how much control you want to give OH2 on a critical system…especially while learning…most users seem to have had unintended effects that rendered OH2 non-operational, if that happens when you are not home, the consequences could be less desirable…when you search the forum, you will find contributions to this…just consider your risk tolerance and your climate (depends on where you live a total loss of heating control can have small or most severe consequences); for me personally, it is one thing if my lights act up or we have to use the hue app when OH2 is in a fritz…but heating and some other system is another thing (again depends on where you live)
As for the rest, a lot of folks here are really passionate about making the docs better; the more specific you can be in terms of what you did not understand, the better; and even more important, this is open-source, if you want to capture your learnings and add to the documentation on github, this would be more than welcome.