I have just bought a (second hand) Bavaria 38 and am completely new to all the mechanics and equipment onboard.
Hi Pip and welcome to the forum.
You've bought yourself a great boat, and I hope you get a great deal of pleasure out of it, but I have to make one comment, what has being "a girl" got to do with anything except as I think Maurice Chevalier put it.
We all have to start at some point, and as the saying goes, the older I get the more I realise that I know less and less about more and more. So now that you have joined the forum, read the various postings that others have made, and in no time at all will become clear.
As for all those levers in the heads, take one line at a time, see what it's connected at the start of its run and where it goes to, and any lever valve fitted between the start and finish will in most instances be a shut off to enable the line to be closed down. Because you also have a holding tank, you will have some three way valves fitted that will allow liquids to be diverted from one destination to another, and in that respect you need to follow each line to see where it goes. Ideally make a drawing of your system on paper and that may well help you to understand what does what.
You mentioned about the "big pipe and its valve," but without seeing what else is connected if anything to that pipe it is not easy to offer an answer.
Regarding a key for the water, diesel and waste caps, a key that would fit can be purchased from your local chandlery shop, though if your boat was second hand when you purchased it, then it's most likely already onboard, but you perhaps have not recognised it for what it is. If you can't find it or have no success at your chandlery shop, then either a very large screwdriver, or a piece of flat plate steel of suitable thickness can be made to fit the groove.
Regarding those "Battery symbols," the bottom two are for your forward and aft fresh water tanks, not the fuel tank where most likely the gauge for that is either on your engine control panel, or very near to it.
The red switch you mentioned correctly is for hot water, but only when you are connected to mains electricity. Otherwise the contents of your hot water tank are heated from the engine cooling water circuit which passes through your hot water tank (more usually known as a "Calorifier"). The hot cooling water from the engine does not mix with the water in your calorifier where instead it runs through a coil or heat exchanger so as to heat the domestic water while remaining completely separated from it.
There's no Bavaria Manual for Dummies as such and so far as I'm aware, but there is this forum which is pretty darn good at making most of us a little more knowledgeable than we were before !!
In one of your other postings you asked a question about posting a photo, and underneath the box where you enter your posting you will see something next to a large plus sign marked Additional Options. Select that and go to where it says Attach, and click on "Choose File." This will then take you to your photo library, the cloud, or give you the option to take a photo. Choose whichever is appropriate, and there you are.
One thing I would say, and that is to join a local sailing club, and you will find lots of people there more than willing to help you discover your boat.
