Driving Car with Trailor Law? Trailor upto 750kg im confused about?

my licence was passed in 2005. It says B and B1 on my licence. Searching on the.gov website it says i can drive upto 3.500kg vehicle and a trailer upto 750kg.

does it mean trailor itself 750kg max of a trailor and whatever loaded on it to a max of 750kg?

so if i drive a ford transit thats approx 2000kg, and my car trailer is 650kg empty, and i have a car on the trailer thats an audi A4 at 1,600kg will i be able to do that on my licence or have to pass a separate test?

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