Also, you may have to break out of aviation texts and go to the library and look up basic principles.
Electrical systems - in small GA are usually DC (Direct Current) electric - find a primer on Electricity and go to the DC section. On bigger airplanes, the system is or may be AC.
Hydraulics - fluid is the same as plumbing for the most part. Pretty simple stuff, but again you can get a textbook on "hydraulic systems" which will give you background into compressibility of fluids, pistons, valves, etc.
Pitot/Static - is again roughly plumbing principles, but now you are using air pressure instead of fluid. Again, a basic text on hydraulics would probably cover some of the background items - especially when they talk about "easily compressible" fluids.
Flight controls - are cables and pulleys - most intro to science books will have a "mechanics" section where you could read about levers and fulcrums, cables and pulleys, etc.
Engine - it's a 4-cycle internal combustion gasoline air-cooled engine. Tons of books on small engines, automotive technology in the library. GA airplane engines are as simple as they come - think more like a lawn mower than a car.
Fuel - back to plumbing and hydraulics.
Retract gear - hydraulics
Brakes - hydraulics
Avionics - radio and electronics - gets really messy in here if you don't have a good strong science background for regular electricity first.
When reading about any systems - remember that the Jepp books are going to show a representative system - something basic and easy to understand. Your POH / Flight Manual should have a manufacturers description of the precise system in the airplane you are using (alas - not with very much detail). From there, you would need to go down to A&P books (general system overview) or Shop Manuals (airplane specific) to see more detail.
Ask a CFI about what is bothering you or talk to a shop guy. It's OK to admit that your not mechanically gifted. My accountant is the smartest money manager on the planet (IMO) - completely inept at figuring out which end of a screwdriver to hold. If you hear an answer that has you completely lost, tell them to explain it again in layman's terms. Eventually, you'll find a common ground.
Another help is the pain old dictionary - especially for words without explanation. For example, I had a student who was not mechanical. The word "manifold" had her completely frustrated. There was an exhaust manifold and there was a manifold on the pitot-static system.
Went to the dictionary:
Manifold - marked by diversity or variety. What???
OK - Manifold (3) - third description of the Noun - a pipe with several lateral oulets for connecting one pipe with others.
Voila! When I explained that the exhaust manifold took one pipe from each cylinder and combined the exhaust into one exhaust pipe - it fits. Then the static line was connected to a manifold so that the airspeed, altimeter and VSI all had static pressure info. Crazy word - lost on a non-mechanical person - seems second nature to someone who is mechanical.
I call this stuff LCD or lowest common denominator teaching. As an instructor, I need to find the area we have in common and then start teaching from there.